Climate of Priest River Experimental Forest, Northern Idaho

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This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. United States Department of Agriculture Climate of Forest Service Intermountain Forest and Range Priest River Experiment Station Ogden, UT 84401 General Technical Experimental Forest, Report INT-159 December 1983 Northern Idaho

Arnold I. Finklin THE AUTHOR CONTENTS Page ARNOLD I. FINKLIN is a meteorologist at the Northern Introduction ...... 1 Forest Fire Laboratory, Missoula, Mont. Specializing in Description of the Area...... 1 climatology, he is currently with the Fire Effects and Stations; Data; Methods ...... 3 Use Research and Development Program. Previous Fire-Weather Data ...... 4 assignments at this location were with Project Skyfire Averages; “Normals”...... 4 and the Fire in Multiple Use Research, Development, Condensed Climatic Summary...... 5 and Application Program. He received a master’s Details of the Climate ...... 6 degree in atmospheric science from Colorado State Precipitation ...... 6 University before joining the laboratory in 1967. Annua| Precipitation ...... 6 Monthly Distribution ...... 8 RESEARCH SUMMARY Daily Precipitation ...... 9 This report describes the climate of Priest River Ex- Snowfall ...... 9 perimental Forest, in the northern Idaho panhandle. Streamflow ...... 10 Primary year-round data are from the “control station” Fire-season Precipitation ...... 11 located at its present site near Forest headquarters Thunderstorms ...... 11 since 1916. The analysis includes temperature and Precipitation Trends ...... 11 precipitation fluctuations or trends. Further details are Temperature ...... 12 provided by fire-weather data, summarized for valley Frost-Free Period ...... 13 and lookout locations. Topographic and local site dif- Temperature Trends ...... 15 ferences in climate are examined, utilizing data ob- Relative Humidity...... 15 tained from past studies in the Forest. Climatic Temperature and Relative Humidity During Fire characteristics at Priest River are found to apply to Season ...... 16 much of the Idaho panhandle area. Wind ...... 18 Wind During Fire Season ...... 18 Cloudiness; Sunshine; Solar Radiation ...... 20 Comparison with Surrounding Area ...... 21 Temperature, Annual Regime ...... 21 Precipitation, Annual Regime ...... 22 Afternoon Temperature, Relative Humidity, and Wind During Fire Season ...... 24 Concluding Remarks ...... 25 Publications Cited ...... 26 Appendix: Detailed Listings and Summaries of Data— Tables 14-33...... 28 Climate of Priest River Experimental Forest, Northern Idaho

Arnold I. Finklin

INTRODUCTION background knowledge of weather and climate may be Established in 1911, the Priest River Experimental gained from Schroeder and Buck (1970); Critchfield Forest, in the northern Idaho panhandle, has long serv- (1974). ed as a field laboratory for research into timber management, genetic improvement of trees, forest insects and DESCRIPTION OF THE AREA diseases, forest fire hazard and control, watershed The Priest River Experimental Forest is located 12 air management, and wildlife habitat (Wellner 1976). (For miles (20 km) north-northeast of the town of Priest brevity, this locale will also be referred to as "Priest River, Idaho, in the Kaniksu National Forest (fig. 1). It River," "the Experimental Forest," or "the Forest.") covers an area of 6,368 acres (2 758 ha). Latitude is Throughout this time, weather data have been collected about 48 '21 ' N; longitude, mostly 116'45' to 116"501W. to gain knowledge about the relevant weather and climatic factors. Climate and weather not only affect the BRITISH COLUMBIA trees directly, acting as controls on their growth and the \1 distribution of forest types, but also influence the ef- -I fects of fire, insects, and diseases. Many of the studies Metaline Falls Porthlll eBonners Ferry at Priest River up to 1950 are described in detail by Wellner and others (1951). For an extensive listing of WASH INGTON eKallspell Newport publications reporting research results, see Wellner Heron 2 NW (1976). MONTANA Studies on the relationship of weather or climate to fire danger and occurrence include those by Larsen and Delavan (1922), Gisborne (1925, 1931), and Hayes (1941). Relationships between climate and forest types or cover are presented by Jemison (1934) and Larsen (1930, 1940). In the field of watershed management, Packer (1962, 1971) and Haupt (1979) have studied the effects of altitude, aspect, and forest cover on snow accumulation and melt. Additional references are mentioned and quoted in the course of this report. / The first comprehensive summary of Priest River climatological data was presented by Jemison (1932a); l DAHO tables covering 50 years of data were prepared by Doty OREGON (1961). The present report updates and expands upon these summaries, for the purpose of providing information of use to forest researchers and managers in the Experimental Forest and adjacent areas; climatic similarity with adjacent northern Idaho is examined. Topographic and local site variations in climate are included. This report does not cover climate-related or derivative factors such as soil temperature, evaporation, fuel moisture, and fire-danger indexes. Measurements of the first two factors have been largely limited to earlier years and are included by Jernison (1932a). Because our objective is to present climatic informa- Figure 1.-Location of Priest River Ex- tion, physical or technical explanations have been large- perimental Forest (PREF), Idaho, and adja- ly assigned to references. Where needed, elementary cent stations mentioned in text. Situated near the southern end of the Selkirk Moun- heterophylla-Abies grandis) and subalpine fir (Abies tains, on a generally westerly slope, the Experimental lasiocarpa). About two-thirds of the forest cover is over Forest has an elevational range from about 2,220 ft to 100 years old. nearly 6,000 ft (675 to 1 825 m). The mountainous ter- Since its establishment, there have been no large rain is cut by Canyon Creek and Benton Creek, leaving wildfires within the Experimental Forest other than the ridges that run in a generally east-west direction (fig. 2). Highlanding Fire in 1922 (Wellner 1976); this burned The Experimental Forest contains most of the forest 400 acres (160 ha). There were close calls from the cover types of the Northern Rocky Mountains. The 18,000-acre (7 300-ha) Quartz Creek Fire in 1926 percentage-area distribution has changed with time, due (Gisborne 1927) and the 31,000-acre (9 450-ha) Freeman to cutting, disease, insects, and natural succession. Lake Fire in 1931 (Jernison 1932b). These fires came Western white pine (Pinus monticola) was, for many within 1 to 2 miles of the Experimental Forest. The Sun- years, the most abundant timber type; now (Wellner dance Fire in 1967 did not threaten this Forest but oc- 1976) the dominant types are western larch-Douglas-fir curred as close as 7 miles (11 km) to the north; it burned (Larix occidentalis-Pseudotsuga menziesii) and Douglas- more than 50,000 acres (20 000 ha) in 9 hours (Anderson fir, followed by western hernlock-grand fir (Tsuga 1968).

Figure 2.-Topography of Priest River Experimental Forest and locations of stations or measurement places mentioned in text. Elevation contours (labeled in hundreds of feet) are drawn at 500-ft (152-m) intervals, except for dashed lines at 100-ft (30-m) intervals. HQ denotes control station at headquarters; CC, clearcut, or fire-weather station site; HC, half-cut site; FT, full-timbered site; BD, Benton Dam; BS, Benton Spring; GIs, Gisborne Lookout; EXP, Experimental Lookout. 27N, 27S, 38N, 38S, 55N, and 55s are altitude-aspect station sites on north (N) and south (S) slopes at 2,700, 3,800, and 5,500 ft (825, 1 160, and 1 675 m) elevation. BF is original control station (1912-16) on Benton Flat; SW and NE, southwest and northeast slope stations during same years. SC denotes end points of Benton Spring snow course (dashed line); TR, transect for snow studies. Benton Meadow snow course is in HQ vicinity. STATIONS; DATA; METHODS The year-round precipitation data have been augmented by measurements at two additional stations Station locations, past and present, are included in (figs. 4A and 4B)—located at Benton Dam (2,650 ft figure 2. The year-round data summarized in this report [808 m]) and near Benton Sp'ring (at 4,775 ft [1 455 m]); are primarily from the "control" weather station, records date from 1941 and 1960, respectively. The located near the Experimental Forest headquarters amounts at Benton Dam—from a weighing-type record building (figs. 3A and 3B); elevation is 2,380 ft (725 m). ing gage—were compiled from U.S. Weather Bureau This station has been at its present site since 1916; the (1964), original forms, and "Hourly Precipitation Data" original control station was 0.25 mi (0.4 km) to the west- summaries published for Idaho. The amounts for Benton northwest—in a former clearing on Benton flat—at a Spring—read monthly from a storage gage—were obtain similar elevation. The recorded data are based on a ed mostly from an annual publication, "Storage-gage 24-hour period ending at 5 p.m. P.s.t., the daily observa Precipitation Data for the Western United States," tion time. Such a long, continuous record at the same discontinued in 1977. More recent data for this station site is exceptional in the Northern Rocky Mountains. and Benton Dam were provided by Priest River annual There has, however, been some change in the immediate reports (for example, Carpenter 1979) and personal com surroundings due to growth of trees. The station was in munication from Mr. Calvin L. Carpenter, Superintend the center of a clearing in earlier years (Jemison 1932a), ent of Priest River Experimental Forest. but now the forest edge is much closer. This report also utilizes monthly snowpack data- Most of the control station data through 1977 were depth and water content—from snow-survey courses ad obtained from a magnetic tape provided by Dr. Myron joining Benton Spring and Benton Meadow (near the Molnau, State Climatologist, University of Idaho, control station), published by the Soil Conservation Ser Moscow. With this tape, 10-day summary tables were vice, as well as streamflow data recorded at Benton produced by computer programs described by Bradshaw Dam. The latter were obtained from Stage (1957) and (1981). Further data were hand-tabulated from the Forestry Sciences Laboratory, Moscow, Idaho. The "Climatological Data" monthly summaries for Idaho, year-round monthly temperature averages at mountain- published by the National Oceanic and Atmospheric Ad top level have been estimated from those at two former ministration (NOAA) and predecessor agencies such as the U.S. Weather Bureau.

Figure 3.—"Control" weather station, Priest River Experimental Forest. A: Location, near Figure 4.—Additional stations at Priest River headquarters building. B: Close-up view; Experimental Forest. A: Benton Dam precipitation gages toward left—weighing- precipitation and stream-gaging station; B: type gage on platform, thermometer shelter Benton Spring precipitation gage, storage in center. type with wind shield.

3 stations—Mullan Pass, Idaho, and Mount Spokane, Wash.—obtained, respectively, from U.S. Weather Bureau (1964) and "Climatological Data" monthly sum t.T maries for Washington. Fire-Weather Data Climatic details for the fire season were obtained from tapes at the National Fire-Weather Data Library, Fort Collins, Colo. (Furman and Brink 1975), used with the computer programs of Bradshaw (1981); also from original fire-weather observation forms filed at the Northern Forest Fire Laboratory, Missoula, Mont. The data include relative humidity, wind, and lightning ac tivity, as well as temperature and precipitation. In the Priest River valley area, the fire-weather data base covers the months May through October. The observa tions were begun in 1922; official records were irom the control station until 1945, thereafter from the clearcut flammability-station site (Hayes 1941). This location (figs. 5A and 5B) is 2,800 ft (850 m) southwest of the control station and 80 ft (25 m) lower in elevation. Observations were discontinued in 1978. Comparative data have been summarized for the continuing fire- weather (or fire-danger rating) station 17 miles (27 km) to the north-northwest at Priest Lake Ranger Station (fig. 5C), elevation 2,590 ft (790 m); the station was located 4 miles (6 km) further north prior to 1964. Until about 1970, the observation season at Priest Lake generally covered only the months June through September. Fire-weather data, limited to July-August, are also summarized for Gisborne Mountain Lookout (figs. 6A- D), which maintained observations from 1933 until 1978. (This lookout was named Looking Glass prior to 1951.) Elevation at the tower base is 5,595 ft (1 706 m), but the weather station (except for wind measurements) was on slightly lower ground to the southeast. The mountaintop observations were originally taken at Ex perimental Lookout, 5,983 ft (1 824 m), which was located at the southeastern tip of the Forest, 1.4 miles (2.2 km) from Gisborne; records date from 1917 (Larsen 1922a) to 1932. The fire-weather observation time was at 4:30 or 5 p.m. P.s.t. in earlier years and near 3 p.m. from about 1950 through 1973, after which it was changed to 12 noon. The respective changes were made in accordance with regional and national standards. Until the late 1940's, observations were also made in the morning at 8 a.m. Our examination of topographic and local site varia tions in climate utilized recording charts from former altitude-aspect and flammability stations (Jemison 1934; Hayes 1941; Wellner 1976). These charts, from the 1930's, are filed at the Northern Forest Fire Laboratory. Figure 5.—A and B: Fire-weather station in Averages; "Normals" clearcut area, Priest River Experimental Forest; discontinued in 1978. View toward Climatic averages presented in this report include southeast, in 1966 (A); site as it appeared in those for standard 30-year "normal" periods, as adopted 1982, looking north (B). C: Fire-weather sta- by international convention; the normal values are revis tion at Priest Lake, Idaho, at airstrip across ed every 10 years. The 30-year length tends to balance road from Ranger Station. Wind sock and out short-term fluctuations, but actually a longer period anemometer are on pole to left (south- southeast), outside of picture. such as 50 years is desirable for precipitation (World Figure 6.—Views at or from Gisborne Mountain Lookout, Priest River Experimental Forest. A: Tower, looking west. B: Fire-weather station, discontinued in 1978, as it appeared in 1982. Site is short distance southeast of tower. C: View to north, showing Priest Lake and Sundance Mountain (right). D: View to south.

Meteorological Organization 1967) and has thus been time of year. The large-scale factors here include lati employed here. A 20-year data sample, however, has tude, relative position on the North American continent, been used for averages (and frequency distributions) for prevailing hemispheric wind patterns, and extensive some of the fire-weather elements; plotted 10-day values mountain barriers. Small-scale or local factors include have been smoothed. This shorter length is based on the topographic setting and position (valley, slope, or availability of data at an unchanged observation time. ridge location), as well as orientation or aspect, and In other cases, adjustments of short-term averages to vegetative cover. Elevation may cover various scales. longer (or standard) periods have been made, based on Broadly, the Priest River-Idaho panhandle climate is the "ratio method" for precipitation and the "difference transitional between a northern Pacific coastal type and method" for temperature. These methods, described fur a continental type. The Pacific influence is noted par ther by Oliver (1973), use comparisons with adjacent ticularly by the late autumn and winter maximum in stations having the full length of record. cloudiness and precipitation; also in the relatively Detailed listings and tabular summaries of data are moderate average winter temperatures, compared with given in the appendix. Further climatic details for Priest areas east of the Rocky Mountains. Summer is River and the surrounding northern Idaho area may be characteristically sunny and dry, though July and found in tables presented by the Pacific Northwest August are the only distinct summer months. July and River Basins Commission (1968). August are thus also the peak fire-danger months. Annual precipitation (rain and melted snow) averages CONDENSED CLIMATIC SUMMARY 32 inches (817 mm) at the Forest headquarters; about 50 The climate of the Priest River area, like that of other inches (1 270 mm) at locations near 5,500 ft (1 675 m) places, is controlled by a combination of large-scale and elevation. Wettest months are normally November, small-scale factors, whose effects may vary with the December, and January. Close to 60 percent of the an nual total occurs during the period November through March. A slight, secondary peak in precipitation normal- nearby above the treetops, about 6 milh (10 kmlh); at ly appears in May and June, followed by a sharp mountaintop locations, about 9 milh (15 krnlh). decrease in July. Snowfall accounts for more than 50 Two summers of continuous wind recording at percent of the total precipitation at elevations above Gisborne Lookout showed highest average speeds 4,800 ft (1 460 m). Snow cover usually persists in the around midnight, between 10 and 11 milh (17 kmlh); a valley from early December through the end of March; minimum in late morning. This pattern is nearly op- seasonal maximum depth averages 30 inches (75 cm). posite of that observed in the valley. High-elevation snowpack reaches a depth of 5 ft (1.5 m) Sunshine duration is at a minimum in December, when or more in March and April and may linger into June. it may average only 20 percent of the maximum possi- The main season of lightning (or thunderstorm) activi- ble, giving a monthly total of about 50 hours; this is ty extends from late May through August. Storms occur estimated from adjacent stations. July has close to 80 within the Priest River vicinity on an average of 3 or 4 percent of the maximum possible, with about 375 hours days each in June, July, and August. of sunshine in fully exposed locations. Monthly mean temperatures at headquarters range A basic statistical summary of the climate is given in from 24" F (-4" C) in January to 65" F (18" C) in July; table 1. these are midpoint values between the average daily maximum and minimum temperatures (based on a 5 DETAILS OF THE CLIMATE p.m. observation time). The annual mean is 44" F (7" C). Precipitation A large diurnal range occurs in summer, with July maximum temperatures averaging 83" F (28" C); January ANNUAL PRECIPITATION maximums average 30 " F (-1" C). Site differences in the Annual precipitation (rain and melted snow) at Forest valley, as related to coverage by timber canopy, can headquarters averages 32 inches (817 mm), based on the make a difference of close to 10" F (6" C) in summer- 50 years 1931-80. A listing of the monthly and annual time diurnal range. Extreme temperatures have been as amounts for each year of record is given in table 14 (ap- high as 103" to 105" F (about 40" C) and as low as -36" pendix); successive 10-year averages and 30-year nor- F (-38" C). Temperature inversions are commonplace, mals are summarized in table 2. Ten-day averages and particularly on the clear summer and early autumn extremes are shown in table 15 (appendix). Water-year nights. The July mean temperature at Gisborne Lookout (October-September) totals have ranged from 17 inches is only 4 " F lower than at headquarters (3,200 ft [975 m] (442 mm) in 1976-77 to 47 inches (1 188 mm) in lower in elevation), due to daily minimums averaging 4" 1973- 74. Ten-year (decadal) annual averages have ranged F higher. from 26 inches (650 mm) during 1921-30 to 34 inches The frost-free season, defined as the period with (861 mm) during 1951-60. A 40-year comparison shows minimum temperatures staying above 32" F (0" C), has annual precipitation averaging about 2 percent greater an average length in the valley of 96 days at head- at Benton Dam, 1.3 miles (2.1 km) to the east. quarters but only 65 days in a clearcut area (at the The Benton Spring storage gage, near 4,800 ft (1 460 former fire-weather station); close to 120 days under a m), indicates a relatively small elevational increase in full timber canopy. The season is longer at adjacent precipitation, with the annual total here averaging slope locations, particularly in the "thermal belt" 37 inches (950 mm). The Benton Spring snow survey around 3,500 ft (1 070 m), but is less than 100 days data, however, indicate that the gage catch is too low. again at 5,500 ft (1 675 m). For example, the average snowpack water content for Relative humidity is usually high throughout the day 1963-77 (latest 15-year period used by the USDA Soil in late autumn and winter, averaging 70 to 80 percent Conservation Service for comparative purposes) shows or higher in midafternoon. In July and August, after- an increase of 5.6 inches (142 mm) during January and noon values average near 35 percent in the valley and 3.8 inches (97 mm) during February; the corresponding 45 percent at 5,500 ft. Humidity below 20 percent was average precipitation inside the gage was only 4.6 inches observed in the clearcut on about 20 percent of the days (117 mm) and 2.9 inches (75 mm), respectively. from late July to late August. Summer nighttime Gage catch can easily be reduced by wind (Hayes humidity in the valley typically recovers to over 90 or 1944)-particularly in the case of snow (Wilson 1954; 95 percent by dawn. On the slopes above the Linsley, Jr. and others 1958), but the Benton Spring temperature inversion, at the same time, humidity may gage site (fig. 4B) is rather sheltered. The gage itself is average only 50 to 60 percent. equipped with a standard shield to reduce wind effects. Winds in this area have a prevailing (most frequent) A possible alternate explanation is interception of wind- direction from the southwest during all or most of the borne snow by the sheltering trees. On the snow course, year. Local terrain effects modify the larger-scale wind there is a noticeable variation in snowpack between that occurs in the adjacent free atmosphere. A night- measuring points (from which an average is obtained), time drainage effect is indicated in the headquarters although this is attributed to differences in canopy area by a prevailing early morning wind direction from situated more directly overhead (communication from the northwest during the fire-weather season. Observed Calvin L. Carpenter). An adjustment of the Benton windspeeds are quite low throughout the year in the Spring precipitation, as described below, gave an annual valley area, due in part to the sheltering by surrounding average of 42 inches (1 070 mm). timber. Summer afternoon winds at 20 ft (6 m) above Much heavier precipitation is indicated, by snow ground in the clearcut average 3 to 4 milh (5-6 kmlh); surveys, to the east in the Schweitzer Basin ski area, O) 00 lO CO CO CD T- CO CO i- JB9A co ^ i^ co «*• r- r^ co r*- m o on o O) O) o O) O) Oi O)

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7 Table 2.-Ten-year (decadal) and 30-year "normal" average precipitation, inches, Priest River Experimental Forest control station Period Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Annual

Decade 1912-20 (9 years) 1921-30 1931-40 1941-50 1951-60 1961-70 1971-80

30 Years 1912-40 (29 years) 1921-50 1931-60 1941-70 1951-80

6 to 7 air miles (10 km) from Benton Spring (see later close to 5.0 inches (125 mm) in December. Extreme section). Within the Experimental Forest, an annual monthly totals have reached 11 inches (285 mm). A average of about 50 inches (1 270 mm) is indicated at slight secondary peak occurs in May and June, followed 5,500 ft (1 675 m), based on 4 years of intensive snow by a sharp decrease to the summertime minimum in sampling (Packer 1962); an adjustment has been made July and August. Monthly amounts then average for the abnormally high snowpack during this period, around 1.0 inch (25 to 29 mm). The averages shown for 1949-52. The seasonal maximum water content at this Benton Spring include an adjustment for the suspected elevation averaged 37 inches (940 mrn). The correspon- deficiency, mentioned above. The adjustment, limited to ding average at 4,800-ft (1 463-m) locations was 23 in- the snow season, used a smoothed curve of ratios of ches (585 mm); it was actually a few inches more than Benton Springlheadquarters monthly precipitation based this at Benton Spring (with snowpack about 25 percent on 22 years; the ratios-initially relatively low in above normal). winter-were extrapolated upward from those in spring and early autumn. About 59 percent of the annual MONTHLY DISTRIBUTION precipitation at headquarters is received during the The pattern of monthly precipitation (fig. 7) shows a months November through March; the proportion is 60.5 decided peak in late autumn-early winter. Amounts at percent at Benton Spring using the adjusted averages, Priest River headquarters average 4.0 inches (100 mm) only 56 percent using the observed gage catch. or greater in November, December, and January, with

7r Benton Spring 6 - -ADJUSTED QAQE CATCH - 5 OBSERVED PRECIPITATION - 4 ------3 ------==--- =------2 ------1 ------0 ------

Headquarters

PRECIPITATION 4 Figure 7.-Monthly average precipitation, Priest River Experimen- tal Forest. Lower panel: At headquarters (control station), based 3 on 50 years 1931-80; snowfall (open bars) is plotted on scale 3"Z- 2 (right side) proportional to that of precipitation, ass.uming an 20 A- average of 1.0 inch water equivalence from 12.0 inches snowfall. 1 z 10 g Upper panel: Near Benton Spring (4,800 ft), 22 years of storage Z 0 0 * gage data adjusted to 1931-80 (hatched bars or portions of bars); JFMAMJJAS OND averages further adjusted for deficient gage catch of snow are MONTH shown by shaded bar extensions. DAILY PRECIPITATION Seasonal snowfall totals at headquarters have ranged Frequencies of various daily precipitation amounts at from 26 inches (66 cm)-most recently in 1976-77-to headquarters are shown in table 16 (appendix). The max- 154 inches (391 cm) in 1949-50. Monthly totals have imum on record for any day (5 p.m. to 5 p.m.) is been as high as 89 inches (226 cm) in January 1969; 2.4 inches (61 mm) in November 1959; Benton Dam only 2 inches (6 cm) fell during January 1981. Maximum received 2.5 inches (63 mrn) during a different 24-hour l-day snowfall of 20 inches (51 cm) occurred in period in the same storm. These amounts are well below December 1951; %day snowfall reached 25 inches (64 the 24-hour maximum expected according to maps by cm) in January 1951. Miller and others (1973); they show 3.6 inches (91 mm) Annual snowfall probably averages over 300 inches for a 100-year period and 3.0 inches (76 mm) for only a (760 cm) at a 5,500-ft (1 675-m) elevation. Here, it con- 25-year period. tributes about 55 percent of the annual precipitation Maximum l-hour precipitation at Benton Dam is sum- (based on stations in the northern half of Idaho [Finklin marized in table 3. The extreme for the 40-year period, 19831). 1941-80, is 0.90 inch (23 mm), recorded in both June Snow Cover; Snowpack.-In an average season, the 1948 and July 1958. This amount is somewhat higher headquarters area has about 120 days with 1 inch or than that calculated for a similar period using the above more of snow cover. The number of such days has reference; a l-hour extreme of 1.0 inch (25 mm) is varied from 152 in 1935-36 to 35 in 1980-81. The period calculated for a 100-year period. A 6-hour extreme of 1.5 of continuous, day-to-day, cover has a median duration inches (38 rnm) occurred at Benton Dam in December from December 5 to March 30. This cover has begun as 1961. The cool-season precipitation, nevertheless, occurs early as November 10, 1931, and has remained as late as with relatively low l-hour maximum amounts; it ac- April 18, 1975. Snow cover was present during the en- cumulates over long durations. For the years 1941-66, tire month of January in all but 2 of the 50 years Benton Dam had an average of 147 hours in both 1931-80 and throughout February in all but 4 years. December and January with 0.01 inch (0.25 mm) or But in 1981, there was practically none during these two more, compared with 19 hours in July and 27 hours in months. August. Snow depth at headquarters (table 4) has been as great as 54 inches (137 cm), in January 1969, compared SNOWFALL with an average seasonal maximum of 30 inches (75 cm). Annual snowfall at headquarters averages 88 inches The maximum occurs more frequently in February than (225 cm), based on the years 1931-80. This amount in January. At the Benton Spring snow course, the represents the sum of individual daily accumulations, depth usually peaks in March or April; it averages close before melting or settling occurs. The monthly average to 5 ft (1.5 m) on the March 1 and April 1 monthly snowfall is included in figure 7; the averages are plotted survey dates. A record depth of 93 inches (236 cm) was on a scale such that their approximate water equivalent measured in 1956, on March 1. The snow lasts well into may be compared with the total precipitation (shown by May here and into June at higher locations. Water con- the shaded bars). For this purpose, we assumed an tent on April 1 at Benton Spring averages 20 inches overall snowfall density of 0.083-that is, 1.0 inch (25 (515 mm). To the east, water content averages 31 inches mm) of water in 12.0 inches (30.5 cm) of newly fallen (785 mm) at Schweitzer Bowl (at a similar, 4,800-ft snow, though much variation can be expected between [l 463-m] elevation) and 48 inches (1 215 mm) at individual storms. A similar average density has been Schweitzer Ridge (6,200 ft [l 890 m]). found elsewhere (Landsberg 1958). Detailed measurements cited by Wellner and others Monthly and annual amounts for each year (or snow (1951) show much less snowpack on south-facing slopes season) of record are listed in table 17 (appendix). than on north-facing slopes- particularly toward late December and January are usually the snowiest months, season (March and later). The ground becomes bare with 50-year averages of 25 and 29 inches (63 and 74 about a month earlier on the south slopes at lower and cm), respectively, at headquarters (table 1). Even so, middle elevations; perhaps 2 weeks earlier on the south figure 7 indicates that over half of the December slope at 5,500 ft (1 675 m). Consistently more snow was precipitation here occurs as rain; almost half in January. indicated in forest openings than under timber, except Overall, about 23 percent of the annual precipitation is near the time of disappearance. Larsen (1940) showed contributed by snowfall. similar slope-related differences, comparing lower-slope

Table 3.-Monthly maximum 1-hour precipitation, inches, at Benton Dam, Priest River Experimental Forest, during 40 years 1941-80

Item Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Annual

Median 0.15 0.15 0.15 0.13 0.17 0.20 0.19 0.21 0.15 0.15 0.15 0.15 0.37 Highest .40 .32 .28 .28 .50 .90 .90 .52 .81 .29 .27 .29 .90 Year 1966 1972 1958 1961 1978 1948 1958 1964 1942 1961, 1942 1961 1948, 1970 1958 Table 4.-Average snow depth (D) and snowpack water content (W), at end of month; maximum snow depth (Max D) during month; Priest River Experimental Forest

Location, period of record Oct. Nov. Dec. Jan. Feb. Mar. Apr. May

Control station, 1931-80 D * I 3 12 20 19 5 0 1912-81 MaxD 5 21 41 54 51 50 28 Year 1919 1915 1964 1969 1969 1916 1917 Benton Meadow, 1937-80 W 2.8 5.0 6.2 3.2 0 Benton Spring, 1937-80 D 12 3 1 47 55 56 36 0 W M2 8.4 13.7 18.2 20.4 15.4 0

=Occurrence too rare for meaningful average. *M =Missing; not measured.

stations having southwest and northeast aspects. Eleva- evident. Overall, 32 percent of the total runoff occurs in tion, aspect, and canopy effects on snowpack are analyzed May; 53 percent in April and May combined. The by Packer (1962), using statistical methods. Packer average date of peak runoff is May 4; median date, May (1971) also analyzes the effects on snowmelt. 10. The peak has occurred as early as February 26, in 1958, and as late as May 29, in 1962. The springtime STREAMFLOW peak flows are analyzed in detail by Haupt (1968). The streamflow (or runoff) regime of Benton Creek is For the 950-acre (385-ha) drainage area above Benton compared in figure 8 with that of precipitation. (The Dam, annual runoff averages about 1,275 acre-ft precipitation, based on the 50 years 1931-80, is within 1 (157 ha-m), from a discharge rate averaging just 1.8 ft3ls percent of its average for the 34 years, 1940-73, of (0.05 m3ls); the rate averages 6.6 ft% (0.19 msls) in May. available runoff data.) The effect of water storage in Highest daily average discharge was 22.6 ft3ls (0.64 snowpack and subsequent release with snowmelt is very mats) on April 27, 1952. Depth of runoff distributed

Figure 8.-Comparison of average water-year regimes of precipitation and runoff in Priest River Experimental Forest. AVERAGE MONTHLY Precipitation is a two-station average, from control station and Benton Spring, based on or adjusted to 50 years Si-N '\ A PRECIPITATION 1931-80. Runoff is that of Benton Creek, measured at Benton Dam, during 1940-73. Monthly and cumulative monthly amounts are in percentage of water-year total. ONDJFMAMJJ

MONTH 10 uniformly over the drainage would be 16 inches (400 in late August, with little further change during mm), or about 40 percent of the areal average precipita- September; then, an upward trend to wet late autumn tion of close to 40 inches (1 000 mm). About 24 inches conditions. Although July and August are normally dry, (600 mm) of this precipitation is apparently utilized in large variation can occur from one year to another and evapotranspiration. Annual runoff depth has varied from between decades (tables 2 and 14). At the control sta- 6.0 inches (153 mm) in water year 1944 to 25.3 inches tion, the 2-month precipitation totaled 0.3 inch (8 mm) (643 mm) in 1956. in 1967; 6.4 inches (163 mm) in 1978. The water-year runoff has only a fair correlation with Ten-day averages and frequencies are presented also water-year precipitation at the control station; the for Priest Lake Ranger Station and Gisborne Lookout, 34-year correlation coefficient, r, was 0.71. Using in tables 18 and 19 (appendix); these cover a shorter September-August, September-June, or October-June season and some of the periods have incomplete data. precipitation, r was 0.78 to 0.79. Dividing the precipita- Overall, the July-August precipitation at Priest Lake tion into seasons, Stage (1957),with 16 years of data, averages about 10 percent greater than at the Priest obtained a multiple regression having a correlation coef- River control station. For the same months, Gisborne ficient of 0.92. Lookout receives about 25 percent more than the control station. FIRE-SEASON PRECIPITATION Ten-day details of valley-area precipitation (taken from THUNDERSTORMS tables 15 and 16, appendix) are given in figure 9; these The main season of lightning (or thunderstorm) activi- cover the official fire season, May through October, and ty extends from late May through August (fig. 9, top about a month before and after. Much of the irregularity panel). During this time, storms within about a 20-mile seen in the averages and frequencies, even with 50 years (32-km)distance occur on about 10 to 15 percent of the of data, is probably accidental. The broader features days. Thus, July and August, the peak fire-danger show the large decrease in precipitation that usually months, each have an average of 3 days with storms commences around early July and a moderate increase observed at the valley location; 4 days at Gisborne Lookout. Detailed lightning observations at this lookout during 1956-71 for Project Skyfire, Northern Forest PRIEST RIVER THUNDERSTORM OCCURRENCE Fire Laboratory, showed that 73 percent of the July- August storms began between 12 noon and 12 midnight, A. - 4'Y 10 /.J '. \--./'i. P.s. t. Based on 15-minute counts of cloud-to-ground v, I' L. t. a 0 I I I I 1 -.-I.-.- 1 discharges during 1960-7 1, the Lightning Activity Level n MJJASON ?5 (LAL) as defined in the National Fire Danger Rating 1111111 System (Deeming and others 1977) was 2 on 51 percent of the thunderstorm days (or on 6 percent of all days). LAL was 3 on 21 percent of the storm days; 4, on 7 percent; 5, on 21 percent.

PRECIPITATION TRENDS Precipitation trends or fluctuations during the past 70 years are depicted in figure 10, using two forms of smoothing. These employ 11-year running means and 5-year weighted means, both representing overlapping 1.40 lo-DAY PRECIPITATION sequences of years. The first form gives equal weighting 1.20 L to each year's data; the second, portraying short-term fluctuations, applies successive weighting of 1, 4, 6, 4, and 1. Values are plotted as percentages of the 1931-80 average. The graphs of annual precipitation show the well- known dry period centered in the 1920's and 1930's. Analyzing tree rings in northern Idaho, Leaphart and Stage (1971) found that this period represented the most AMJJASOND 111111111 adverse growth conditions for western white pine in DATE three centuries. Following a recovery centered in the 1950's, an overall downward tendency is indicated in Figure 9.-Average regimes of 10-day more recent years. The "winter" (November-March),late precipitation and thunderstorm occurrence, Priest River Experimental Forest head- spring (May-June),and summer (July-August) graphs quarters area (control station); based on 50 also show dry conditions in the 1920's and 1930's, but years 1931-80. In bottom panel, totals for they display some opposing tendencies since that time. 11-day periods have been adjusted to 10 days. For example, May-June precipitation was rather high in the 1940's (opposite of the winter pattern), then declined until very recently; while July-August precipitation MAX.

MIN.

IIIIIIIII~I~I JFMAMJJASONDJ

MONTH

Figure 11.-Average daily maximum ana YEAR minimum temperatures at valley and moun- Figure 10.-Precipitation fluctuations during taintop locations, Priest River Experimental 70 years since 1912 at Priest River Ex- Forest; based on 24 hours ending at 5 p.m. perimental Forest, control station. Eleven- and 30-year normal period, 1951-80. Moun- year running means (solid lines) and 5-year taintop averages are estimated (see text). weighted means (dashed lines) are plotted at midpoint years (for example, the means for 1970-80 and 1973.77 are plotted at 1975). minimums range from 18" F (-8" C) to 47" F (8" C). Monthly mean temperatures-taken as midpoint values between the maximum and minimum-are thus 24 " F shows an irregular increase into the 1950's, then an ex- (-4" C) in January and 65" F (18" C) in July; the annual ceptional increase during the 1970's. The 5-year mean is 44" F (7" C). These means are based on 24-hour weighted mean summertime precipitation centered maximum and minimum data observed at 5 p.m. P.s.~., around 1976, 1977, and 1978 was nearly 200 percent of and may be about 1" F higher than means based on ac- the 1931-80 average; this mean had been as low as 25 tual calendar-day data or individual hourly readings (ex- percent in the early 1930's. planations are given by Rumbaugh 1934; Baker 1975). Graphs representing stations farther south in northern At 5,500 ft (1 675 m), the monthly means range from Idaho and extreme eastern Washington (Finklin 1983) about 20" F (-7" C) to 61" F (16" C)-only a few degrees show similar precipitation characteristics. For earlier lower than those at headquarters. This small elevational years, these graphs indicate a relatively wet period near decrease reflects the presence of temperature inversions. the beginning of this century. These are mainly a nighttime phenomenon but also affect daytime temperatures in autumn and winter. Temperature Inversion effects on daytime (or maximum) The normal yearly course of temperature is portrayed temperature are greatest in December and January, in figure 11, for both headquarters and a 5,500 ft (1 675 when, most often, a warmer airmass aloft may override m) elevation. Averages at this mountaintop level have cold air entrenched in the valley. Conversely, the been estimated from those atop Mount Spokane, Wash., daytime temperature decrease with elevation, or "lapse and Mullan Pass, Idaho, at about 5,900 to 6,000 ft rate," is generally strongest in spring; average max- (1 800 to 1 835 m). The estimates-adjusting for eleva- imums at 5,500 ft (1 675 m) then run 13" or 14" F (7 " or tion and period of record-were tuned to be consistent 8" C) below those at headquarters. The difference is 1" with the July and August averages from Gisborne or 2" F less in July and August. On the other hand, dur- Lookout. ing these two months and early autumn, nighttime For the normal period, 1951-80, average daily max- inversions-from radiational cooling favored by clear imum temperatures at headquarters range from 30" F skies (Schroeder and Buck 1970)-result in lower average (-1" C) in January to 82" F (28" C) in July; average minimum temperatures at headquarters than at 5,500 ft. Temperatures for each year of record at the control weather station (before its ternhation in 1978) and at station, through 1982, are listed in table 20 (appendix); Priest Lake. Data from five adjacent climatological sta- successive 10-year averages and 30-ye& normals, in tions give a corresponding increase averaging only 0.5" table 5. Ten-day averages and extremes are shown in F relative to 1961-70; 1.5" F since 1951-60, though this tables 2 1, 22, and 23 (appendix); frequency distributions ranges from 0.4" F at Sandpoint to 2.7" F at Newport. of daily values, in tables 24 and 25 (appendix). The cold- est month of record is January 1937, with a mean of FROST-FREE PERIOD 6.5" F (-14" C), including an average minimum of -4.4" As shown in table 7, the control station has an F (-20" C). The warmest month is July 1975, with 70.4" average length of 96 days between last-spring and first- F (21" C), resulting from a high average minimlm; tht autumn minimum temperatures of 32" F (0" C) or lower. highest average maximum, 90.7" F (33" C), occurred in The respective average threshold dates are June 4 and August 1967. Extreme maximum for any day is 103" F September 8. There is an average length of 137 days (39" C) recorded in August 1961-the clearcut (fire- between occurrences of 28" F (-2" C) or lower. These weather) station reached 105" F (41" C); the minimum is temperatures are usually reached under fair-weather -36" F (-38" C) in December 1968. The extremes show a conditions-by radiational cooling-and are accompanied smaller range at higher elevations. Mount Spokane, by frost formation. Wash., had -28" F (-33" C) in December 1968; Gisborne The frost-free season is shorter at the clearcut site, Lookout, 95" F (35" C) in August 1961. averaging 29 days shorter between dates of 32" F. For For most months of the year, the 1971-80 average both the 32 " F and 28 " F thresholds, the season at minimum temperatures (table 5) show an increase over valley locations may average close to 2 months longer those during 1961-70 and preceding decades; the in- under a full timber canopy than in the clearcut. This is crease is particularly large in July and August, about 3" indicated by 6 years of recording charts from the former F (1.5" C). Possibly up to 1.0" F of this summertime in- flammability stations. Four years of charts indicate an crease may be a result of a change that occurred in even longer season without freezing temperatures at the observation practice-using a hygrothermograph trace, former 2,700-ft (823-m) and 3,800-ft (1 160-m) altitude- rather than actual maximum and minimum thermometer aspect stations. The season becomes short again at readings, to obtain the daily temperature extremes. highest elevations, as shown in table 7 for Mount There may thus be effects of slower response often Spokane and Mullan Pass, at 5,900 to 6,000 ft (1 800 to found in hygrothermographs, as well as possible bias in 1 835 m); it may be about 2 weeks longer than this at calibration. 5,500 ft (1 675 m). The threshold occurrences at these A comparison in table 6 shows that the 3 " F increase elevations are oftenqwith blustery conditions, sometimes in control station minimum temperature was slightly with late-spring and early-autumn storms that bring greater than that observed at the Priest River fire- snow.

Table 5.-Ten-year (decadal) and 30-year "normal" average daily maximum and minimum temperatures, OF, at Priest River Experimental Forest control station

Period Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.Annual

Decade 1912-20 Max. (9 years) Min. 1921-30 Max. Min. 1931-40 Max. Min. 1941-50 Max. Min. 1951-60 Max. Min. 1961-70 Max. Min. 1971-80 Max. Min. 30 Years 1931-60 Max. Min. 1941-70 Max. Min. 1951-80 Max. Min. Table 6.-Station comparison, by decades, of average daily maximum and minimum temperatures, OF, observed during July and August

Station' and daily observation time2 PREF PRFW PLFW BONF CDAL NEWP PTHL SAPT 5STA Period 17 153 153 174 17-15 17-15 17' 17

.------.-----Average temperature, July and August combined------1951-60 Max. 81.3 83.1 83.2 85.7 84.8 83.2 80.1 83.4 Min. 44.9 42.0 48.7 51.3 43.8 48.1 47.7 47.9 1961-70 Max. 82.5 83.4 83.0 86.0 85.4 82.4 81.0 83.5 Min. 45.4 43.0 49.0 52.5 45.8 49.0 48.2 48.9 1971-80 Max. 81.7 83.1 84.7 84.0 80.9 80.8 82.7 Min. 48.1 42.5 49.9 52.9 46.5 49.8 48.1 49.4 1964-70 Min. 45.2 42.7 40.6 1971-77 Min. 48.0 44.7 42.2

~PREFdenotes Priest River Experimental Forest Control Station; PRFW, Priest River fire-weather station (ter- minated after 1977); PLFW, Priest Lake fire-weather station (location since 1964); BONF, Bonners Ferry, Idaho; CDAL, Coeur d'Alene, Idaho; NEWP, Newport, Wash.; PTHL, Porthill, Idaho; SAPT, Sandpoint, Idaho; SSTA, average of five preceding stations. 2~imebased on 24-hour clock; thus 17 denotes 5 p.m. local time. 3~imechanged to 12 in 1974. 4Time changed to 07 in 1975.

Table 7.-Freezing temperature thresholds, OF. Observed dates of last occurrence in spring (or until July 31) and first occurrence in autumn (or after July 31), Priest River Experimental Forest valley area and adjacent mountain stations

Date1 of last Date of first Number of days spring minimum autumn minimum between dates 24O 28O 32O" 32' 28' 24O 24O 28O 32O or lower or lower or lower

Priest River control station, 50 years 1931-80: Mean 411 7 Standard dev., days 13 Median 411 9

Earliest, 311 7 year 1958 Latest, 511 1 year 1959 Maximum, year Minimum, year

Priest River fire-weather station (clearcut), 28 years 1946-73: Mean 5118 6/19 8123 9/10 Difference, days2 +6 +14 -15 -11 Median 5119 6118 8/23 9110

Mullan Pass, Idaho (10 to 15 years during 1942-57) and Mount Spokane, Wash. (12 years during 1959-72); two-station average: Mean 511 2 616 6123 919 9121 1015 146 107 78 Median 519 618 6126 919 9122 1015

'Month numberlday number; thus 4117 is April 17. 2~eandate minus that at control station during same years. TEMPERATURE TRENDS 1930's, but this excess is due to the higher minimum Past trends or fluctuations of temperatures at the con- temperatures noted earlier-maximum temperatures are trol station are depicted in figure 12. As with precipita- down (table 5). For the above-mentioned area to the tion in figure 10, the observed values have been smooth- south, a graph shows recent July-August means peaking ed; here they are plotted as degree differences from the about 0.5" F above the 1930's level. The 1960's and 1931-80 average. 1970's temperature trends in northern Idaho are con- The graphs-for annual, winter, and summer mean trary to some of the cooling publicized for eastern parts temperatures-all show a warming trend from the begin- of the United States. This difference may follow from ning of record until about 1940; this is generally concur- the east-west spacing between prevailing upper-air rent with the notable period of below-average precipita- trough and ridge locations. tion (fig. 10). Graphs for an area to the south (Finklin 1983) indicate that this warming trend had begun only a Relative Humidity few years earlier. The 11-year annual and summertime Relative humidity is recorded continuously throughout means in that area varied little for at least 30 years the year on hygrothermograph charts at the control sta- prior to the 1910's; wintertime means rose 4" F (2" C) tion, but the data have not been tabulated; accuracy is from about the mid-1880's to 1900, then fell 2" F (loC) uncertain, particularly during winter. Available year- by the early 1910's. After 1940, figure 12 shows a cool- round humidity averages, based on psychrometer ing until about 1950 to 1955; since then, to date, an readings, cover only the period prior to 1919 and a 5 overall warming for the year and summer-this has oc- p.m. P.s.t. observation time. Otherwise, humidity data curred without the dry conditions of the 1930's. The for Priest River are limited to the fire-weather season- more irregular winter temperature pattern indicates an with readings at 8 a.m. and 5 p.m. until about 1950; overall decline since the early 1960's. once-daily at 3 p.m. in subsequent years. In the valley Recent 11-year July-August means at the control sta- these data are from the clearcut site beginning in 1945. tion have been about 1.0" F higher than those of the The general annual pattern of relative humidity may be obtained from figure 13. Afternoon averages at Priest River (valley location) are shown, together with afternoon and early morning averages elsewhere in the North- ern Rockies; both a valley and a ridgetop location are TEMPERATURE represented. Relative humidity tends to vary inversely

ANNUAL

JULY-AUG. 1 ALISPELL ULLAN PASS OF- I OPRIEST RIVER.6 P.m. m JFMAMJJASOND

MONTH

YEAR Figure 13.-Graphs of monthly average Figure 12.-Temperature fluctuations during relative humidity at 4 a.m. (A) and 4 p.m. (P) 70 years since 1912 at Priest River Ex- at Kalispell, Mont., airport (based on years perimental Forest, control station; based on 1950-70) and Mullan Pass, Idaho (1950.54 averages of observed daily maximum and data adjusted to longer period). Superimpos- minimum values. Eleven-year running means ed are averages for Priest River Experimental (solid lines) and 5-year weighted means Forest, valley area, at 4:30-5:00 p.m. (based (dashed lines) are plotted at midpoint years. on 1921-50, except 1912-18 for March) and at 3 p.m. (based on 1951-70). Times are P.s.t. with temperature (Schroeder and Buck 1970), and this rainfall seen in figure 9. With an elevational difference of largely accounts for the diurnal differences seen in this about 3,280 ft (1 000 m), the temperature differences in- fig&; also for higher afternoon values at higher eleva- dicate an average summer afternoon lapse rate of 4.0" F tions. The 3 p.m. averages at Priest River, during May per 1,000 ft (7.3 " C per 1,000 m) between the valley bot- through October, are generally similar to the afternoon tom (clearcut area) and the lookout. As shown later, averages shown for ~Ais~ell,Mont.; higher values occur however, temperatures at intervening slope locations can at Priest River by 5 p.m., particularly in late season. vary several degrees or more from lapse-rate estimates. Early morning humidity in the Priest River valley area Further temperature and humidity details are given in probably averages higher throughout the year than at tables 26 and 27 (appendix). Noteworthy is the combina- Kalispell; it averages above 90 percent in summer, as tion of extremely high afternoon temperature and low seen later. As inferred from figure 13, relative humidity relative humidity that persisted during the 10-day period in the Experimental Forest is high throughout most August 11-20, 1967-the year of the Sundance s ire run, days during November through February, averaging 70 north of the Experimental Forest (Anderson 1968). The to 80 percent or higher in midafternoon. With a slight lowest recorded daily humidity value at Priest River, 5 interruption in the showery month of June, the after- percent, occurred in August 1961. noon average decreases sharply during spring, reaching Percentage frequencies (or probabilities) of various July-August levels of about 34 percent in the valley. temperature and humidity values are graphed in figure 15. Again, the curves reveal a turn toward summertime TEMPERATURE AND RELATIVE HUMIDITY levels near the end of June. Occurrence of a midafter- DURING FIRE SEASON noon relative humidity below 30 percent in the valley Figure 14 shows the trends of midafternoon has a 23 percent chance in midJune; a 62 percent temperature and relative humidity during the fire chance by late July. Additional details are given in season. Even with smoothing, the 10-day averages show tables 28 and 29 (appendix). a pronounced change near the end of June, toward the Combined frequencies of temperature and relative warm and dry conditions peaking in mid-July to mid- humidity, together with windspeed, are given in table 30 August. hi; change corresponds with the decrease in (appendix). The frequencies of values beyond certain

100 r DRY BULB, OF

60 GISBORNE LOOKOUT

lW [ RELATIVE HUMIDITY,PCT 1

1 1 1 1 1 1 1 DATE I 1111111111111111111 I M J J A S 0 N Figure 14.-Ten-day average dry bulb 1 1 1 1 1 1 1 temperature and relative humidity at 3 p.m. DATE P.s.t. at valley and mountaintop locations, Figure 15.-Ten-day frequencies of specified Priest River Experimental Forest; based on dry bulb temperature and relative humidity at years 1951-70. Curves are drawn through 3 p.m. P.s.t. at valley and mountaintop loca- smoothed values plotted at middle of tions, Priest River Experimental Forest; based 10-day period; smoothing used 1-4-1 on years 1951-70. Curves are drawn through weighting applied to original values of three smoothed values, as in figure 14. consecutive periods. limits, rather than within the classes shown, may be ob- humidity, fuel moisture, wind, and evaporation. After- tained by appropriate summation. noon relative humidity in the clearcut averaged 9 per- Ten-day details are also given (tables 31 and 32, ap- cent lower than in full timber; 2 percent lower than in pendix) for average daily maximum and minimum the half-cut area. A summary of measurements nearby temperatures. The Priest River data-from the clearcut at "open, one-third cover, and uncut" locations in July- area-differ somewhat from those in tables 16 and 17 August 1919 is given by Larsen (1922b; 1924). (appendix) for the control station; the frequency distribu- A contrast between the original control station and tions (not shown) also differ. Periods of record are dif- two nearby, lower-slope stations-at about 2,500 ft (762 ferent, but the site differences are the main factor. For m) elevation-is shown by Larsen (1940); data covered the same 20-year period, 1951-70, July-August max- the years 1912- 16. Maximum temperatures during the imum temperatures averaged 1.3" F lower at the control May-September period averaged 4.5" F (2.5" C) higher station than in the clearcut; the minimums, 2.6" F on a southwest slope than on a northeast slope; after- higher. noon relative humidity, 7 percent lower. Overall, during Topographic and Local Site Effects.--Further local and the year, minimum temperatures on these slopes aver- topographic variations in temperature are summarized in aged 4" or 5" F (2" to 3" C) higher than on the flat. table 8. This tabulation utilizes data from fire-weather Diurnal Variation of Temperature and Humidity.-The observation forms and also the recording charts for the average daily course of temperature during July-August 1930's altitude-aspect and flammability stations. The at low and high elevations is depicted in figure 16; averages, though based on only four summers, relative humidity, in figure 17. As noted in the legends, demonstrate that temperatures at a slope location do not the curves are based on available recording charts cover- necessarily fit a simple elevational gradient or lapse rate. ing only a few years; they do, however, give averages Local surroundings are an important consideration in ad- compatible with long-term afternoon and early morning dition to aspect. The thermal belt described by Hayes data. The contrast seen between locations illustrates (1941) is a few hundred feet below the 3,800-ft earlier comments about diurnal range, nighttime inver- (1 160-m) elevation. Here, near the average nighttime in- sion effects, and the dependence of relative humidity on version top, minimum temperatures during July-August temperature. The curves show the warmest, driest time averaged as much as 15" F (8" C) higher than at the of day is usually between 2 and 4 p.m. P.s.t. The fire- clearcut site. A similar inversion and thermal belt was weather observation time of 3 p.m., used prior to 1974, detected by a mobile survey described by Schaefer (1957), which also found large contrasts in dewpoint temperature. The inversion magnitude may average about half as large during the more cloudy, showery months of May and June (Hayes 1941). Average July- August temperatures at headquarters were very similar to those at the half-cut site in table 8. The clearcut, half- cut, and full-timber sites show notable differences in diurnal temperature range-differences amounting to as much as 9" F (5" C)-but have a close similarity in monthly mean temperature. Jemison (1934) presents maximum temperatures at these three sites during July-August 1933, showing differences similar to those in table 8. He also reveals large differences in soil temperature, duff temperature, relative

Table 8.-Comparison of average temperatures, OF, in Priest River Ex perimental Forest during study by Hayes (1941);data for July and August combined. 1935-38

Minimum, Maximum, Station, elevation (ft) overnight daytime Mean

MID 02 04 06 08 10 12 14 16 18 20 22 MID Lookout, 5,580 TIME, P. s. t. 5,500, N aspect 5,500, S 3,800, N Figure 16.-Average diurnal course of 3,800, S temperature, July-August, Priest River Ex- 2,700, N perimental Forest. Curve for control station 2,700, S is based on averages from recording charts Control, 2,380 at clearcut site, adjusted to smaller diurnal Clearcut, 2,300 range. Curve for 5,500 ft uses several years Half-cut,2,300 of charts from Looking Glass (now Gisborne) Full-timber, 2,300 Lookout and 1937.38 charts from north- aspect and south-aspect stations. humidity averages practically the same-within + 1

loo HEADQUARTERS percent-at the two stations in June, July, and August, but 3 percent higher at Priest Lake in September; humidity at the earlier Priest Lake station averaged about 5 percent higher in July-August. Table 9 also indicates higher windspeeds at Priest Lake, which can be expected from its more open station location (fig. 5C). Wind Average windspeeds observed in the Priest River- northern Idaho area are summarized in figure 18. Com- parability among the available stations is affected by differences in period of record and anemometer height- the present standard (Fischer and Hardy 1976) is 20 ft (6 m) above open, level ground or nearby treetops. Nevertheless, figure 18 shows some distinct features. I , , , , , , , , , , , , , I The graph for Mullan Pass indicates that on exposed MID 02 04 06 08 10 12 14 16 18 20 22 MID high terrain, windspeeds may average highest in winter; lowest, in July and August. This is the tendency of the free-atmosphere wind, above the mountainous Figure 17.-Average diurnal course of topography and its local effects, as indicated on normal relative humidity, July-August, Priest River upper-air maps near 10,000 ft (3 000 m). In contrast, in Experimental Forest. Curve for control sta- the sheltered valley area at headquarters, 24-hour tion is based on 1935-39 recording charts average speeds at 8 ft (2.4 m) above the ground are very from former half-cut flammability station. light throughout the year, with the least wind in autumn Curve for 5,500 ft is based on stations used and winter. in figure 16. Prevailing. (most frequent) wind direction was from the southwest or south during most of the year at Mullan thus tended to represent the afternoon extreme condi- Pass; northwest in summer. At the control station, the tions. At the observation time now in use throughout prevailing direction during daylight hours is the Northern Rockies, 12 noon P.s.t. (1 p.m. m.s.t.), it southwesterly year-round. In comparison, average wind can be seen that temperatures in the Priest River area in the free air near 10,000 ft (3 000 m) is from the west may average 2" or 3" F (1.5" C) lower than previously; or west-northwest in winter, west-southwest in summer. relative humidity, perhaps 5 percent higher. Comparison with Priest Lake Fire-Weather Data.- WIND DURING FIRE SEASON Because fireweather observations are no longer taken at In the Priest River area, figure 18 indicates that sum- Priest River, a comparison of past data may aid in mak- mer afternoon windspeeds on the mountaintops average ing estimates from the continuing observations at Priest 8 or 9 milh (13 to 14 kmlh); the same average applies for Lake Ranger Station. This station has been at its pre- a 24-hour period. In the valley, afternoon speeds during sent site since 1964. (Earlier data were observed 4 mi [6 May through August average near 3.5 milh (6 kmlh) in km] further north.) Table 9 shows average differences in the clearcut; 6 milh (10 kmlh) at 150 ft (45 m) above observed values during 1964-73; also the differences ground and well above surrounding treetops. These prior to 1964 to indicate effects of the Priest Lake sta- valley averages decrease in September and October. The tion change. Overall, during June through September, speeds at 150 ft are similar to those observed at the the afternoon temperature at Priest Lake averages 1" F Priest Lake Ranger Station airstrip. Combined frequen- . lower than at the Priest River clearcut site. The relative cies of afternoon speeds and directions are presented in

Table 9.-Differences in average temperature, relative humidity, and windspeed at Priest Lake Ranger Station (PL) and Priest River Experimental Forest, clearcut site (PR)

Difference, PL minus PR, during 1964-73 (and during 1951-63, in parentheses, at previous PL location) Relative Humidity, Temperature, OF percent Wind, milh Month At 3 p.m. Minimum at 3 p.m. at 3 p.m.

June - 0.7 - 2.8 + 0.7 + 2.7 July - 0.7 (- 1.O) -2.4 ( 0.0) - 0.7 (+ 4.8) + 3.2 (+ 2.3) August -1.2 (-1.1) -2.1 (-0.1) - 0.1 ( + 5.6) +3.2 (+2.2) September - 1.6 - 2.2 + 3.2 + 2.3 MLP b, GIS i , (3- 5 p. m. Z

150 FT ABOVE GROUND

I IIIIIIIIIIIII MID 02 04 06 08 10 12 14 16 18 20 22 MID

TIME, P. s. t.

11111l1~~1~~~Figure 19.-Average diurnal course of wind- J FMAMJJAs-ONDJ speed during July-August, Priest River Ex- MONTH perimental Forest; atop 150-ft tower near Figure 18.-Average windspeed for 24-hour headquarters (based on years 1938-40), and period or midafternoon observation time, as at Gisborne Lookout (based on 1942 and noted in parentheses, Priest River Ex- 1944). Heavy dots denote average 8 a.m. and perimental Forest (PREF)-northern Idaho 5 p.m. speeds at 150 ft (based on 1931-44, in- area. At Mullan Pass (MLP), based on years cluding data from former exposure on tower- 1950-54; PREF headquarters (HQ), at 8-ft ing treetop). Open circles denote average 8 height, based on 1912.36, and 150.ft height, a.m. speeds (during 1933-47) and 3 to 5 p.m. 1924-33; PREF fire-weather station (in clear- speeds (during 1933-60) at Lookout. cut, CC) and Priest Lake Ranger Station (PL), nighttime air drainage down the Priest River Valley. 1951-70; Gisborne Lookout (GIs), 1933-60; Ex- perimental Station Lookout (EXP), 1926-32. Even so, at least at this daylight hour, this wind direction occurred on only 45 percent of the July-August days; south or southwest, on 32 percent. The prevalence table 33 (appendix);the directions, at both valley and of southwest and south winds in the afternoon may be lookout locations, are predominantly from the southwest. enhanced by a daytime upvalley breeze (Schroeder and Frequencies of windspeeds may also be obtained from Buck 1970). table 30 (appendix). The mountaintop windspeed pattern in figure 19 dif- As indicated in figure 19, winds in the valley area fers from that shown by Hayes (1941) for a median day typically decrease in late afternoon and evening. Atop in August, 1936-38. His diagrams, using measurements the 150-ft (45-m)tower, average speeds were down to 3 7.5 ft (2.3 m) above ground, portray an afternoon max- milh (5 kmlh) from about 10 p.m. to 6 a.m. during July- imum at all elevations on slopes up to 5,500 ft August. At Gisborne Lookout, at over 50 ft (15 m) (1 675 m). This maximum is greater on south slopes than above ground, chart recordings available for two summers on north slopes, possibly as a result of greater upslope often showed a wind increase during the evening, giving breeze and also greater exposure to the larger-scale highest average speeds- 10 milh (16 km1h)-at around wind. The maximum speed shown at 5,500 ft was 6 milh midnight; the wind reached a minimum at around 10 (10 kmlh); nighttime speeds were down to 3 or 4 milh in a.m. At this time, the speed was nearly the same as in contrast with speeds of 10 milh (16 kmlh) in figure 19. the valley above the forest canopy. Nighttime wind in- Differences in anemometer height could possibly explain creases have been characterized for mountaintop loca- the difference in afternoon speeds (Ayer 1960). tions (Baughman 1981). Though such increases do not An examination by decades reveals a peculiar decrease show up everywhere (Court 1978), they have previously in windspeeds observed at Gisborne Lookout. Table 28 been noted in averages obtained at two lookouts in (appendix) for this station is thus based only on the southern Idaho (Hanna 1933). years 1951-60, rather than 1951-70. The afternoon Nighttime wind directions do not appear to change speeds averaged 10.0 milh (16 kmlh) in July-August much on the mountaintops; 8 a.m. winds at Gisborne 1933-40; 9.0 milh in 1941-50; 8.5 milh in 1951-60; 6.1 during July-August 1933-40 were from a southerly milh in 1961-70. The most recent decrease seems too quadrant (S, SW, or SE) on 76 percent of the days. At large to be explained by natural variation. The the headquarters location, prevailing 8 a.m. wind direc- anemometer has remained exposed atop the lookout tion during 1931-44 was from the northwest, suggesting (fig. 6A and communication from Calvin L. Carpenter). A change in instrument (from 4-cup anemometer to a more Cloudiness; Sunshine; Solar Radiation accurate 3-cup type) may account for some of the decrease in The period late autumn through early winter is the earlier years. cloudiest time of year; summer, the clearest. The month Extreme July and August windspeeds shown by ly average numbers of days characterized as clear, partly Hanna (1939) reached 49 mi/h (79 km/h) at Gisborne cloudy, and cloudy at Priest River are listed in table 1. Lookout; this was the maximum 5-minute average Such observations were recorded and published until recorded at any time of day during an 8-year period in 1948. The three categories are based on cloud cover, the 1930's. The individual monthly extreme values sunrise to sunset, averaging 0 to 3 tenths, 4 to 7 tenths, averaged 32 mi/h (52 km/h). Near headquarters at 150 and 8 to 10 tenths, respectively. The average numbers of feet (45 m) above ground, the corresponding values clear days range from 5 each in November, December, recorded during a 5-year period were 29 mi/h and 23 and January to 19 in July and August; the numbers of mi/h (47 km/h and 37 km/h). cloudy days, from 4 in July to 22 in December. More Local Site Effects.—The reduction of windspeed within cloudy days and fewer clear days are noted at the a dense timber stand is shown by Gisborne (1941). nearest airport stations, which record such days on the Measurements were made near headquarters on the basis of hourly observations. For example, Kalispell, 150-ft (45-m) tower, which was constructed in the 1930's Mont., Lewiston, Idaho, and Spokane, Wash.—drier loca (Fitzgerald 1958) (fig. 20). Wind at 2 ft (0.6 m) and 49 ft tions than Priest River—all have averages of only 2 or 3 (15 m) heights, under the canopy, averaged only 1 or 2 clear days in December and January; 25 or 26 cloudy mi/h on the windiest days. Speeds on these days were days in December. Part of the difference may lie in near 15 mi/h (24 km/h) atop the tower, which was about classifiying days with high, thin (cirrus-type) clouds 50 ft (15 m) above the surrounding trees at that time. through which the sun can shine. Differences in windspeed related to local exposure or Actual sunshine information for this area is lacking. aspect are shown by Larsen (1940), using 24-hour data A solar-radiation recorder has been in operation at the recorded 9 ft (2.7 m) above ground. Wind during the control station for many years, but data tabulations period May-September averaged 2.9 mi/h (4.7 km/h) on a from the charts are not available. Estimated values are southwest slope near headquarters; 0.9 mi/h (1.4 km/h) thus presented, based on adjacent station data; also on m a northeast slope; 1.7 mi/h (2.7 km/h) on the flat. maps from Environmental Science Services Administra tion (1968). These maps can, of course, give only an ap proximation in mountainous areas. The estimated monthly percentages of maximum possi ble sunshine are shown in figure 21. These range from about 20 percent in December to nearly 80 percent in July. For a location with level horizons and no shading by trees, the percentages would translate into totals of about 50 hours of sunshine during December and 375 hours during July; about 2,500 hours for the entire year. The incoming solar radiation—the solar energy received with sunshine and also through cloud cover—is estimated in figure 22. The values refer to radiation as received on an unobstructed horizontal surface at lower elevations. Values include the direct-beam radiation and the diffuse, or scattered, radiation (Reifsnyder and Lull 1965, Schroeder and Buck 1970). The average monthly totals (curve "a") range from near 2,500 langleys (gm-cal/cm2) in December to 19,000 langleys in July. The annual aggregate is about 125,000 langleys. Curve "b" indicates the radiation that may be received on the clearest days, free of haze. For conversion to units of Watt h/m2, the numbers of langleys are multiplied by 0.0861. Within the Experimental Forest, differences from the above values can be expected according to slope aspect and angle; also due to local surroundings that block or reflect sunshine. Generally more radiation should be received on the mountaintops than in the valley bottom (Geiger 1965). The elevational difference in radiation loss, by absorption in the atmosphere above, is an im portant factor. Figure 20.—The 150-ft meteorological The effects of slope are greater in winter than in sum tower within timber stand near head- mer. During December and January, a south-facing 30° quarters, Priest River Experimental Forest, (58 percent) slope may receive nearly twice as much total as it appeared in 1982. lllllllllllll 0 DEC. J F M A M JUNE J A S 0 N DEC. DEC. J F M A M JUNE J A S 0 N DEC. 15 15 15 MONTH MONTH AND DATE

Figure 21.-Monthly average percentage of maximum possible sunshine duration, Figure 22.-Annual regime of solar radiation estimated for Priest River Experimental (direct and diffuse) estimated for Priest River Forest. Experimental Forest, lower-elevation location; langleys (gm-callcm*) per day received on unobstructed horizontal surface. Vertical marks represent midmonth.

radiation (direct and diffuse) as a horizontal surface. A Temperature, Annual Regime north-facing 30" slope may receive one-half as much radiation as the horizontal and all of this will be diffuse. Table 10 lists the monthly and annual mean These estimates utilize direct radiation data obtained temperatures at the valley locations. These means, which from Buffo and others (1972). During July, the 30" average the daily maximum and minimum values, offer a south slope should receive about the same total radia- comparison that tends to reduce the influences of local tion as the horizontal; the north slope, perhaps 80 per- exposure and related differences in diurnal temperature cent as much. range; such differences have already been shown between sites at Priest River. Stations have been grouped into COMPARISON WITH SURROUNDING two forest areas in figure 23. Panel A indicates that the monthly mean temperatures at the control station are AREA generally 1.0" to 1.5" F (about 0.7" C) lower than those Although this report has focused on the Priest River based on six other stations in the Kaniksu vicinity. Experimental Forest, the climatic description may apply Most of this difference could be attributed to the higher also to a larger area of the Idaho panhandle, where the valley floor at Priest River, 345 ft (105 m) above the forests are similar. The panhandle area lies within a average elevation for the six stations. The elevational ef- broadly similar climatic region, though horizontal gra- fect is countered very little by effect of latitude; the dients and local, topographic variations do occur. This average location of the six stations is at a point just 14 final section examines how closely some climatic miles (23 km) northeast of Priest River. statistics at Priest River compare with those at other Noticeably larger temperature differences are seen in a available stations. Year-round data are based on a comparison with four stations in the Coeur d'Alene-St. 30-year normal period and are limited to valley (or can- Joe vicinity; the overall elevation is similar to that at yon) locations. the control station. In this case, the geographic location, Table 10.-Monthly and annual mean temperatures at Priest River Experimental Forest control station and at adjacent valley or canyon stations in Idaho panhandle, except as noted; based on 30-year normal period, 1941-70 (EF denotes Experimental Forest and RS denotes Ranger Station)

Mean Temperatures Station, elevation (ft) Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Annual

Priest River EF 2,380 Avery RS (former loc.) 2,492 Bonners Ferry, 1 SW 1,850 Coeur d'Alene RS 2,158 Heron 2 NW, Mont. 2,240 Metaline Falls, Wash.' 2,107 Newport, Wash. 2,135 Porthill 1,775 Saint Maries 2,145 Sandpoint Exp. Sta. 2,100 Wallace, Woodland Park 2,950

'Based on 23 or 24 years to 1965.

averaging 68 miles (110 km) south-southeast of Priest PREF/KAN River, could account for about 1.0" to 1.5" F (about 0.7" ANNUAL C) of the difference (based on average gradients in the free amosphere near 10,000 ft [3 000 m]). In table 11, the monthly temperatures are expressed relative to the annual mean. Although the actual monthly means differ between locations, the similarity in this table indicates that the shape of the annual curve at Priest River is typical for the Idaho panhandle. Precipitation, Annual Regime MEAN TEMPERATURE Table 12 lists the monthly and annual average PREF-KAN precipitation. As indicated in figure 23B, amounts at the Priest River control station average somewhat higher ANNUAL than the overall average for valley locations in the Idaho panhandle. Amounts are about the same, however, at nearby Sandpoint and are slightly higher at valley (or ------$ ------L ----ANNUAL 0 *-* canyon) stations to the southeast, near Avery, Heron, ----I ---. .** and Wallace. Table 13 compares the cumulative monthly precipitation, expressed in percentage of water-year -4.0 1 PREF-CSJ total. The resulting distributions at Priest River and 1 11111!111111 ONDJ FMAMJ JAS over the larger Kaniksu and Coeur d'Alene-St. Joe areas are nearly identical. MONTH At higher elevations, snow surveys indicate that much Figure 23.-Comparison of monthly average of the Idaho panhandle has heavier precipitation than temperature and precipitation at Priest River Priest River Experimental Forest. As noted earlier, at Experimental Forest control station (PREF) approximately 4,800 ft (1 463 m), the April 1 snowpack and adjacent valley or canyon stations in water content at Schweitzer Bowl averages 31 inches Kaniksu National Forest vicinity (KAN) and (785 mm), compared with 20 inches (515 mm) at Benton Coeur d'Alene-St. Joe National Forests vicinity (CSJ); based on 30-year normals, 1941.70. Spring. At the four other snow courses near this eleva- Panel A: Temperature differences, PREF tion, the corresponding water content averages between minus KAN (six-station average), solid line, 30 inches (755 mm) at Copper Ridge, east of Coeur and PREF minus CSJ (four-station average), d'Alene, and 49 inches (1 240 mrn) at Smith Creek, dashed line. Panel 6: Precipitation ratios, northwest of Bonners Ferry; the latter amount implies PREF to KAN and CSJ station averages. about 80 inches (2 000 mm) annual precipitation. Table 11.-Monthly mean temperatures, expressed as differences from annual mean temperature, based on 30-year normal period, 1941-70; at Priest River Experimental Forest control station (PREF) and groupings of stations in Kaniksu Na- tional Forest vicinity (KAN) and Coeur d'Alene-St. Joe National Forests vicinity (CSJ)

------Difference from annual mean Station or grouping Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

lAverage from six stations: Bonners Ferry, Heron, Metaline Falls, Newport, Porthill, and Sandpoint. *~veragefrom four stations: Avery, Coeur d'Alene, Saint Maries, and Wallace (Woodland Park).

Table 12.-Average monthly precipitation at Priest River Experimental Forest control station and at adjacent valley or canyon stations in Idaho panhandle, except as noted; based on 30-year normal period, 1941-70. (EF denotes Experimental Forest and RS denotes Ranger Station)

Average precipitation Station Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Annual

Priest River EF Avery RS (former location) Bonners Ferry 1 SW Coeur d'Alene RS Heron 2 NW, Mont. Metaline Falls, Wash.1 Newport, Wash. Porthill Saint Maries Sandpoint Exp. Sta. Wallace, Woodland Park

lBased on 23 or 24 years to 1965, plus 5 or 6 years at Boundary Dam (located 9 miles to north).

Table 13.-Average cumulative water-year precipitation at end of each month, in percentage of annual total, based on 30-year normal period, 1941-70; at Priest River Experimental Forest control station (PREF) and groupings of stations as in table 11

Cumulative water-year precipitation, at end of month Station or grouping Oct. Nov. Dec. Jan. Feb. Mar. April May June July Aug. Sept.

...... Percent of total ...... PREF 9.7 22.2 35.8 48.9 58.2 66.7 72.9 80.6 88.7 91.5 95.0 100.0 KANA 9.6 22.2 35.3 48.1 57.2 64.9 70.9 78.6 86.9 89.9 94.2 100.0 CSF2 9.3 21.7 34.5 47.8 57.2 65.9 73.0 80.5 88.3 91.1 94.7 100.0

lAverage from six stations: Bonners Ferry, Heron, Metaline Falls, Newport, Porthill, and Sandpoint. 2~veragefrom four stations: Avery, Coeur dlAlene, Saint Maries, and Wallace (Woodland Park).

23 lookouts, which commonly are vacant in early July and Afternoon Temperature, Relative late August-particularly with cool, moist conditions. Humidity, and Wind During Fire Season Calculations show that the temperature (or "dry bulb") July-August average afternoon temperature and at Priest River, clearcut site, averages 0.9" F (0.5' C) relative humidity at fire-weather stations are mapped in lower than at the eight other valley stations (which figure 24; wind, in figure 25. The data, for 1500 P.s.t., average slightly lower in elevation); relative humidity, are based on only a 10-year period, 1961-70, to maximize 0.5 percent higher. Including the 11 lookouts, the overall the number of stations having comparable years of lapse rate of afternoon dry bulb between stations is 4.1" record. The stations are limited to the Kaniksu and F per 1,000 ft (7.5" C per 1 000 m)-close to the rate Coeur d'Alene National Forests and vicinity. (Data found between the Priest River clearcut and Gisborne shown for Spokane, Wash., are not included in the Lookout. Little relationship is found between average calculations.) The 2-month average tends to compensate relative humidity and elevation at the valley stations for unrepresentative averages of the individual months. (which lie within a narrow elevational range), but the For example, August 1961-70 afternoons, overall, were higher averages at adjacent lookouts give an overall in- warmer than normal in the Idaho panhandle (example, crease of 3.5 percent per 1,000 ft (305 m)-near the rate table 5); July 1961-70, near or slightly cooler than nor- of 3.8 percent per 1,000 ft found at Priest River. mal. Adjustments were made for incomplete records at As within the Experimental Forest, summer afternoon winds are from a prevailing southwesterly direction over most of the Idaho panhandle (and adjacent eastern Washington) (fig. 25). Some exceptions are seen, related to local topography (such as intervening terrain and valley or canyon orientation). As shown earlier in the

Newport 2135 29

Newport 2135

Spokane AP 2356

--- 4000 FT ELEVATION CONTOUR

Figure 24.-Summer afternoon average temperature, OF (upper number) and relative humidity, percent, at stations in Idaho panhandle and adjacent Washington; at 1500 P.s.t., average for July and August combined, --- 4000 FT ELEVATION CONTOUR based on years 1961.70. Small numbers below station names are elevations, ft m.s.1. Figure 25.-Summer afternoon average wind- Averages for lookouts (locations shown by speed, milh, and prevailing direction at sta- triangles) have been adjusted for missing tions as in figure 24; based on available data (see text). Averages at Priest Lake (from observations at 1500 P.s.t. during July- 1964-73 data at present station) and Sandpoint August, 1961-70. Directions are shown by ar- (from 1963.70 data) Rave also been adjusted. rows (pointing downwind). comparison with Priest Lake, windspeeds in the Priest CONCLUDING REMARKS River valley area are relatively low. Speeds at the other valley stations averaged generally near 5.0 milh The Priest River Experimental Forest contains within (8.0 kmlh), one-third higher than a$ Priest River. Wind- its 10-mi2 (25-km2)area the climatic characteristics iden- speeds at the 10 surrounding lookouts, at elevations tified with mountainous areas in general; these are averaging 5,615 ft (1 712 m), had an overall average of superimposed upon the characteris tics related to its 6.5 milh (10.5 km1h)-just 0.5 milh higher than the geographic location. Resulting statistics have been Gisborne Lookout average for 1961-70, which earlier presented. In a comparison with adjacent stations, these was found to be rather low when compared with speeds statistics were found to follow the seasonal pattern oc- in previous decades. The lookout windspeeds, while curring over the larger Idaho panhandle area-numerical higher than at adjacent valley locations, show a weak values were also similar in many cases. correlation with elevation (r was 0.36). The highest- Priest River stands out in its history of weather and lookout, on Roman Nose Mountain, did have the highest climatological observations. These have been taken at average speed, 10 milh (16 kmlh). permanent stations and also at a variety of sites as part In summary, the above comparisons indicate that the of various studies. The aggregate of measurements climatic data for Priest River Experimental Forest close- represents the efforts of many persons throughout the ly follow the pattern found over most of the Idaho years. Local effects of elevation, slope, and timber cover panhandle. Numerical values are also similar in many are reflected in the data thus obtained. Our climatic cases, particularly when adjustments are made for eleva- description has borrowed upon much of this resource; tion and latitude differences. Similar local topographic there were additional data not as readily available in effects may be expected. The Priest River valley area, publications or not as yet tabulated into usable form. representing a location with well-timbered surroundings, The findings for Priest River, representing much of adja- does have lower windspeeds than surrounding fire- cent northern Idaho, add to the store of knowledge that weather stations. researchers and managers may draw upon for inferences in forested mountain areas elsewhere. PUBLICATIONS CITED Furman, R. William; Brink, Glen E. The national fire weather data library. Gen. Tech. Rep. RM-19. Fort Anderson, Hal E. Sundance Fire: an analysis of fire Collins, CO: U.S. Department of Agriculture, Forest phenomena. Res. Pap. INT-56. Ogden, UT: U.S. Service, Rocky Mountain Forest and Range Experi- Department of Agriculture, Forest Service, Intermoun- ment Station; 1975. 8 p. tain Forest and Range Experiment Station; 1968. 39 p. Geiger, Rudolf. The climate near the ground. Rev. ed. Ayer, Harold S. The wind profile at the crest of a large Cambridge, MA: Harvard University Press; 1965. ridge. Mon. Weather Rev. 88(1): 19-23; 1960. 611 p. Baker, Donald G. Effect of observation time on mean Gisborne, H. T. Using weather forecasts for predicting temperature estimation. J. Appl. Meteorol. 14(4): forest-fire danger. Mon. Weather Rev. 53(2): 58-60; 471-476; 1975. 1925. Baughman, Robert G. Why windspeeds increase on high Gisborne, H. T. Meteorological factors in the Quartz mountain slopes at night. Res. Pap. INT-276. Ogden, Creek forest fire. Mon. Weather Rev. 55(2): 56-60. UT: U.S. Department of Agriculture, Forest Service, 1927. Intermountain Forest and Range Experiment Station; Gisborne, H. T. A five-year record of lightning storms 1981. 6 p. and forest fires. Mon. Weather Rev. 59(4): 139-150; Bradshaw, Larry S. Climatology software package, 1931. user's guide. In: Systems for Environmental Manage- Gisborne, H. T. How the wind blows in the forest of nor- ment final report, Supplement No. 7, to Fire Effects thern Idaho. Missoula, MT: U.S. Department of and Use R&D Program. Missoula, MT: U.S. Depart- Agriculture, Forest Service, Northern Rocky Mountain ment of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station; 1941. 14 p. plus Forest and Range Experiment Station, Northern figures. Progress Report. Forest Fire Laboratory; 1981. 36 p. plus appendixes. Hanna, R. T. Annual fire weather report for District No. Buffo, John; Fritschen, Leo J.; Murphy, James L. Direct 5, season of 1932. Boise, ID: U.S. Department of solar radiation on various slopes from 0 to 60 degrees Agriculture, Weather Bureau; 1933. 35 p. north latitude. Res. Pap. PNW-142. Portland, OR: U.S. Hanna, R. T. Annual fire weather report for District No. 4, Department of Agriculture, Forest Service, Pacific Nor- season of 1938. Missoula, MT: U.S. Department of thwest Forest and Range Experiment Station; 1972. Agriculture, Weather Bureau; 1939. 45 p. 74 p. Haupt, Harold F. The generation of spring peak flows Carpenter, Calvin L. Priest River Experimental Forest by short-term meteorological events. Bull. Int. Assoc. report, 1979. Ogden, UT: U.S. Department of Sci. Hydrol., 13(4-12): 65-76; 1968. Agriculture, Intermountain Forest and Range Experi- Haupt, Harold F. Effects of timber cutting and ment Station; 1979. 16 p. Unpublished. revegetation on snow accumulation and melt in north Court, Arnold. Diurnal variation of winds at 3 km in the Idaho. Res. Pap. INT-224. Ogden, UT: U.S. Depart- Sierra Nevada. In: American Meteorological Society, ment of Agriculture, Forest Service, Intermountain preprint volume, conference on Sierra Nevada Forest and Range Experiment Station; 1979. 14 p. meteorology; June 1978, South Lake Tahoe, CA; 1978: Hayes, G. Lloyd. Influence of altitude and aspect on 53-54. daily variation in factors of forest-fire danger. Circ. Critchfield, Howard J. General climatology, 3d ed. 591. Washington, DC: U.S. Department of Agriculture; Englewood Cliffs, NJ: Prentice-Hall, Inc.; 1974. 446 p. 1941. 38 p. Deeming, John E.; Burgan, Robert E.; Cohen, Jack D. Hayes, G. Lloyd. A method of measuring rainfall on win- The National Fire-Danger Rating System-1978. Gen. dy slopes. Mon. Weather Rev. 72(5): 111-114; 1944. Tech. Rep. INT-39. Ogden, UT: U.S. Department of Jemison, George M. Climatological summary for the Agriculture, Forest Service, Intermountain Forest and Priest River Forest Experiment Station, 1912-1931, in- Range Experiment Station; 1977. 63 p. clusive. Exp. Stn. Publ. Missoula, MT: U.S. Depart- Doty, Robert D. 50-year summary (1912- 1961) ment of Agriculture, Forest Service, Northern Rocky climatological data, Priest River Experimental Forest. Mountain Forest and Range Experiment Station; Ogden, UT: U.S. Department of Agriculture, Forest 1932a. 27 p. Service, Intermountain Forest and Range Experiment Jemison, George M. Meteorological conditions affecting Station; 1961. 16 p. Office report. the Freeman Lake (Idaho) fire. Mon. Weather Rev. Environmental Sciences Services Administration, En- 60(1): 1-2; 1932b. vironmental Data Service. Climatic atlas of the United Jemison, George M. The significance of the effect of States. Washington, DC: Environmental Sciences Ser- stand density upon the weather beneath the canopy. J. vice Adminstration; 1968. 80 p. For. 32(4): 446-451; 1934. Finklin, Arnold I. Weather and climate of the Selway- Landsberg, Helmut. Physical climatology, 2d ed. Bitterroot Wilderness. Moscow, ID: University Press DuBois, PA: Gray Printing Co., Inc.; 1958. 446 p. of Idaho; 1983. In press. Larsen, J. A. Weather records at lookout stations in Fischer, William C.; Hardy, Charles E. Fire-weather northern Idaho. Mon. Weather Rev. 50(1): 13-14; observers' handbook. Agric. Handb. 494. Washington, 1922a. DC: U.S. Department of Agriculture; 1976. 152 p. Larsen, J. A. Effect of removal of the virgin white pine Fitzgerald, 0. A. A man and his monument. Steelways. stand upon the physical factors of site. Ecology. 3(4): 14(4):24; 1958. 302-305; 1922b. Larsen, J. A. Some factors affecting reproduction after Reifsnyder, William E.; Lull, Howard W. Radiant energy logging in northern Idaho forests. J. Agric. Res. 28(11): in relation to forests. Tech. Bull. 1344. Washington, 1149-1157; 1924. DC: U.S. Department of Agriculture, Forest Service; Larsen, J. A. Forest types of the northern Rocky Moun- 1965. 111 p. tains and their climatic controls. Ecology. ll(4): Rumbaugh, W. F. The effect of time of observation on 631-672; 1930. mean temperature. Mon. Weather Rev. 62(10): 375-376; Larsen, J. A. Site factor variations and responses in 1934. temporary forest types in northern Idaho. Ecol. Schaefer, Vincent J. Atmospheric studies from a moving Monogr. 10: 1-54; 1940. weather observatory. Bull. Am. Meteorol. Soc. 38: Larsen, J. A.; Delavan, C. C. Climate and forest fires in 124-129; 1957. Montana and northern Idaho, 1909-1919. Mon. Schroeder, Mark J.; Buck, Charles C. Fire weather. Weather Rev. 50(2): 55-68; 1922. Agric. Handb. 360. Washington, DC: U.S. Department Leaphart, Charles D.; Stage, Albert R. Climate: a factor of Agriculture; 1970. 229 p. in the origin of the pole blight disease of Pinus mon- Stage, A. R. Some runoff characteristics of a small ticola Dougl. Ecology. 52(2): 229-239; 1971. forested watershed in northern Idaho. Northwest Sci. Linsley, Ray K., Jr.; Kohler, Max A.; Paulhus, Joseph L. 31(1): 14-27; 1957. H. Hydrology for engineers. New York-Toronto- U.S. Weather Bureau. Climatic summary of the United London: McGraw-Hill; 1958. 340 p. States-supplement for 1951 through 1960, Miller, J. F.; Frederick, R. H.; Tracy, R. J. Precipitation- Climatography of the United States No. 86-8, Idaho. frequency atlas of the western United States, volume Washington, DC: U. S. Department of Commerce; 1964. V-Idaho. NOAA Atlas 2. Silver Spring, MD: U.S. 66 p. Department of Commerce, National Oceanic and At- Wellner, Charles A. Frontiers of research-Priest River mospheric Administration, National Weather Service; Experimental Forest, 1911- 1976. Ogden, UT: U.S. 1973. 43 p. Department of Agriculture, Forest Service, Intermoun- Oliver, John E. Climate and man's environment. New tain Forest and Range Experiment Station; 1976. York: John Wiley and Sons; 1973. 517 p. 148 p. Pacific Northwest River Basins Commission, Wellner, C. A.; Watt, R. F.; Helmers, A. E. What to see Meteorology Committee. Climatological handbook, Col- and where to find it on the Priest River Experimental umbia Basin States, 3 volumes. Vancouver, WA: Forest. Misc. Publ. 3. Missoula, MT: U.S. Department Pacific Northwest River Basins Commission; 1968: v. of Agriculture, Forest Service, Northern Rocky Moun- 1, 540 p., v. 2, 262 p.; v. 3, 641 p., plus appendixes. tain Forest and Range Experiment Station; 1951. 86 p. Packer, Paul E. Elevation, aspect, and cover effects on Wilson, Walter T. Analysis of winter precipitation obser- maximum snow accumulation in a western white pine vations in the cooperative snow investigations. Mon. forest. For. Sci. 8(3): 225-235; 1962. Weather Rev. 82(7): 183-199; 1954. Packer, Paul E. Terrain and cover effects on snowmelt in World Meteorological Organization. A note on a western white pine forest. For. Sci. 17(1): 125-134; climatological normals. Tech. Note No. 84. WMO-No. 1971. 208.TP. 108. Geneva: World Meteorological Organiza- tion; 1967. 15 p. APPENDIX: Detailed Listings and Summaries of Data-Tables 14 through 33

Table 14.-Monthly and annual precipitation, 1911-82, at Priest River Experimental Forest control station

Precipitation Year Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Annual

50-year average, 1931-80 4.28 3.10

'T = trace, an amount too small to measure. Table 15.-Precipitation statistics for Priest River Experimental Forest control station; amounts in inches. Mean totals are based on 50 years, 1931-80. Extremes are for 1912-82; listed year (first two digits omitted) is the most recent in cases of more than one occurrence. Number .OO denotes either zero or trace (less than OB05 inch) PRECIPITATION BY 10 (OR 11)-DAY ARD P'10fdTiiLY PERIODS

STATION hbPdNER 107.386 PRIEST kIVEH EXP FOH (CONTROL STN) YP5 1931-1980 EXCEPT AS NOTED

10-DAY AND ROhTHLY TOTALS WAXINUP DAILY TOTALS I 1912-1982 I 1912-1902 P E A h! STG hIGHEST LOWEST I EXTRCME, AVG STD TCTAL CEV MEDIAh TO1 9 YH TOTIYH I Y H MAX OEV MEDIAN I JA~J 1 1.36 099 1.23 3.6123 00020 1 1,2359 5 034 054 JAil 11 1 1.22 1.36 6.1274 .0036 1 1.7467 067 $48 a61 JAlZ 21 136 10 1.08 3.7370 .0080 i 1.6059 057 042 a51 FER 1 1.14 a77 lob9 3.09 49 000 54 I 1.53 49 097 35 a42 FEU 11 1.01 .€39 .A3 3.5870 3 I 1.7370 045 ,37 037 FEb 23. 0.95 067 070 5.4157 a0070 1 1.5358 045 037 a39 MAR 1 0.91 cjb 78 3 .GO65 1 1.9066 043 .33 037 MAP 11 0. $8 73 a 71 3-18 45 .0U 30 I 1.38 50 37 026 032 VAh 21 0.9b a 72 b3 2.7343 oOOh6 I ,9767 040 025 037 APH 1 0.67 055 051 2.17 63 ,00 77 1.17 71 34 .26 .34 APH 11 C.70 a 72 a Q4 2.8437 o0051 I 1.50e2 034 028 027 APR 21 0.64. 56 a 44 2.13 53 .00 77 1 1.16 53 .35 .29 028 MAY 1 0.75 067 a 67 3.4161 .GO71 I 1.0779 -34 022 a28 MAY 11 0.79 87 53 3.58 57 -00 79 1 1.69 41 041 038 033 MAY 21 0.74 a70 43 2.5325 .'JUSC 1 2,0525 a38 036 030 JUIJ 1 0.04 72 070 2.79 47 .OO 65 I 1.51 46 043 038 036 JUR 11 b.01 a70 080 3.10 37 .OO h7 1 1.47 16 041 020 ,44 JUK 21 0.66 64 059 2.74 55 .GO 77 1 1-48 55 0-36 032 a27 JlJL 1 0.43 46 27 1.6698 000 73 1 1.0948 027 026 ,I5 JLIL 11 0.36 052 12 2.11 78 an0 73 1 1.34 37 021 026 010 JUL 21 0.21 029 005 1.2915 oOOOO 1 08757 014 020 004 A 1 C.21 a31 06 1.44 18 a00 01 I 077 19 1 018 oOq AUG 11 0.34 58 06 2.63 68 a00 01 I 1.66 19 020 020 a04 AM 23. 0-61 64 -45 2.6% 26 -00 74 L 1.24 75 .3h 3 .27 SUP 1 0.51 063 *24 2.96 27 -00 73 X 1.62 40 032 a38 013 SEP 11 0.57 58 039 3.44 27 000 75 1 1.65 27 3 033 026 SEF 21 0.51 059 32 2.16 55 .00 79 I 1.16 02 -28 .29 .I9 OCT 1 0.81 090 a 53 3ob1 55 000 80 1 1.75 51 040 043 028 OCT 11 9.77 095 044 4.7847 ,0061 I 1.4546 037 036 032 OCT 21 1.24 1.01 090 3oE250 00065 I 1.5718 ,50 036 042 KOV 1 1.11+ 975 lrC5 4.31 12 000 81 I 1.31 18 -58 034 059 NO\r 11 1.54 1.26 1.35 5.08 73 000 44 I 2.40 59 063 052 054 NUV 21 1-35 a58 1.15 3.6762 000 56 1 1.7590 060 4 050 iiEC 1 1.50 .92 1.34 3.2170 00072 I 1,6441 061. 035 054 DEC 11 1.61 1-52 1-35! 6.60 33 000 76 5 2.21 51 .6Q .50 -56 DEC 21 1.75 1.02 1.64 3.95 37 .oe 30 I 1.30 74 a65 031 063

JAK FER "]Ah" 4PH MAY JUrl JUL. AUG S E F OCT rv 0 V DEC Table 16.-Frequency distribution of daily precipitation amounts at Priest River Experimental Forest control station; based on years 1931 through 1977

P;IECIPITATIOiJ - ktRCE'I'JTAGE FYE.QUENCY OF DAILY AMOUhTS (INCHES) - GI\/Eii TO NEuKEST lEFlTH PEItCEPJT, nEC11~li.L PGIIvT OMITTED

PFIIIOII 3ELIll'> 0.20

J 1 L 3 P J1iri 11 247 JA~I21 217 FCI I L 11 FEL3 11 157 FFI~21 196 fiAt4 I i 77 'I 'I A Y 1 1 177 Nriq 21 *7b APH 1 12f 4P2 11 115 AP.' 21 9 8 M4f 1 132 MAY 11 151) 11Af 23 lUb JIJPl 1 Ih4 JlJPi 11 14 5 Jtll 21 115 JllL 1 b 4 JlJL 1~ 5 1 JllL 21 4 3 A I 3 t: LUG 11 4 Y AUG 21 9 3 SFL' 1 12 SEP 11 9 E SEP ?1 9 1 UCT I 1 b; QCT I1 126 OCT 21 807 ri0v 1 1 d5 10v 11 L77 NOV 21 r3: OEC 3 257 dEC 11 ttb 3EC 21 282

IVir31JTY

JAIJ FEH I'IA i A P'< llAY JlJl I J JL P\ II G SEP QCT 3 \I LIEC

* LESS Th41'd I Table 17.-Monthly and annual snowfall, 1911-82, at Priest River Experimental Forest control station Snowfall Year July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May June Annual

1911-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 19-20 1920-21 21 -22 22-23 23-24 24-25 25-26 26-27 27-28 28-29 29-30 1930-31 31 -32 32-33 33-34 34-35 35-36 36-37 37-38 38-39 39-40 1940-41 41-42 42-43 43-44 44-45 45-46 46-47 47-48 48-49 49-50 1950-51 51 -52 52-53 53-54 54-55 55-56 56-57 57-58 58-59 59-60 1960-61 61-62 62-63 63-64 64-65 65-66 66-67 67-68 68-69 69-70 1970-71 71-72 72-73 73-74 74-75 75-76 76-77 77-78 78-79 79-80 1980-81 81-82 50-year average 1931-80

'M = missing. 2T = trace, an amount too small to measure. 3lncludes estimates for days with missing data. Table 18.-Precipitat ion (inches) during fire season at additional stations in or near Priest River Experimental Forest; statistics based on indicated years PRECIPITATION BY 10 (OH Ill-DAY AND MONTHLY PERIODS

STATION NUI"IB€H 100204 PRIEST LAKE Rase YdS 1951-1980

10-DAY AND MONTHLY TOTALS I MAXIMUM DAILY TOTPLS DERIOD NO, MEAN STD HIGHEST LOWEST I EXTREME AVG STD gEGINS YRS TOTAL i)E V MEDIAN TOT* YR TOT~YRI YR MAX DEV PEDIAN I JUN .464 ,00651 ,8871 a318 .235 a300 JUN ,480 .03 69 I .87 52 .389 .225 .36O JUlJ ,577 ,OO 77 1 .82 67 a313 -260 ,300 J'JL .GO4 .00 73 I 1.28 78 a325 .329 a260 JUL ,394 .!I0 73 I 1.09 56 .226 ,275 .I25 JUL -398 .00 80 I .78 61 ml4F a220 035 9UG .404 .oo 79 T a94 53 a217 ,289 040 AUG .P.99 -00 73 1 1.65 80 a307 a445 a100 AUG .670 ,00741 a9053 a335 274 .270 SEP .426 .00 72 I 1.24 60 a281 .283 -235 SEP .635 -00 76 I 1.55 68 a299 ,347 .215 SEP .632 ,00791 .a272 -318 -287 a280

MONTH JUiU 16 2.011 .798 .537 -187 ,515 JUL 30 1.141 .a62 ,482 .314 ,430 AUG 30 let22 1.343 a534 a413 a450 SEP 19 1.508 .a63 a516 .224 .570

PRECIPITATIO AND RONTHLY PERIODS

STATION NUMBER 100202 GISBORNE LOOKOUT Y3S 1951-1978

10-DAY AND MOYTHLY TOTALS T MAxIPUM DAILY TOTALS PER IOIJ NO. PIE AhJ ST@ HIGHEST LOWEST I EXTREME AVG STD BEGINS Y US TOTAL DEV MEDIAN TOT* YR TOTIYR I YR MAX DEV MEDIAN 1 JUL 1 26 a623 .637 ,355 2.22 54 ,UO 73 I 1-09 54 ,337 a310 .255 JUL 11 28 ,459 .542 .245 1.92 75 ,00 69 T 1.03 75 -275 .312 -175 JUL 21 28 2 7 0 ,372 .060 1.15 55 .OO 73 I .87 58 .I64 a229 060 AUG 1 28 a393 .491 .I90 1.8776 rn007EJ a7053 ,224 a 225 .I50 AIJG 11 28 ,515 a781 .080 2.90#68 .OO 73 T 1.15 78 .222 a310 ,070 AUG 21 16 ,826 .794 a780 2.43 77 .OO 70 I1..28 76 .517 .448 a640

MONTH

JUL a299 r 515 AUG a414 a 640

YRS 1931-1978/ I'ER IGD EEGINS

JUL 1 JUL 11 JUL 21 AUG 1 AUG 11 LUG 21

6 0 FJ T H dULY AIJG

* SUM OF MEANS FOR THE # INCLUDES ESTIMATES FOR MISSING DAYS / IhiCLUDES DATA FKOM FCRNER EXPERIPSENTAL STATIOh LOOKOUT FOR 1931 AND 1932 Table 19.-Frequency distribution of daily precipitation amounts at stations as in table 18

f't?ECIPITATIl)Pl - PEKLErJTAGE FREOIJEIdCY OF DAILY AMOUl'iTS ( INCHES)

- GIVEiV TO RIEARCST TE'JTH FJEIICE;\iTq DECIhAL POINT OMITTED

STATION IIJbi.!jEl( 100204 t'I!IEST LAYE N.S.

PERIOL BEG INS

J!JN 1 JUrJ 11 Jill? 21 JilL 1 JUL 11 Jl.rL 21 AIJG 1 ALIG 11 All6 21 SEP I SEP 11 SF-? 21

FlOTuTH

JlJhl JUL AI?G SEP

PH~CIPITHTIO~, - PEuCtPITr\tit FHFQLJENCY OF GAILY AHOUNTS ( INCHES 1

- 6I\ICyJ TO IJEAPEST TFVTH PE9CEhTq DECIMAL POI'UT OMITTED

STAT JOfd NL,LL

APIOUI'JT EQUAL TO nk GREATER 1hAN

JuL 1 2C1 27 3lL+ ?3r 1'35 111 7 3 5 17 JUL 11 2r1J 29 239 143 121 7 5 5 4 4 6 JUL 21 3 I) r7 16 140 1 ir l 3 4 2 6 15 AdG 1 280 3 225 168 121 49G 6 46 3 6 4UG 11 276 4@ 2rJ7 159 127 7 6 5 4 4 7 435 21 179 F, ?79 723 16& 123 P 9 6 1

JUL 899 20 22b 155 131 7 7 49 3 7 A JG 735 33 231 17P 135 9 1 h 0 4 6 Table 20.-Monthly and annual average temperatures, 1911-82, at Priest River Experimental Forest control station; based on 24-hour period ending at 5 p.m. Pat. Average Daily Maximum and Minimum Temperatures Year Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Annual

Max. Min. 29.9 55.2 14.1 29.1 28.5 55.0 11.0 27.3 35.7 57.0 23.2 30.5 31.O 57.1 17.6 31.9 20.4 53.6 -.5 26.8 29.2 56.2 11.2 29.0 32.9 57.0 21.8 30.5 35.6 55.7 20.2 28.9 31.4 55.0 18.1 31.O

33.7 55.8 20.7 30.5 26.1 55.2 11.2 28.5 34.6 56.9 22.0 31.2 27.4 56.6 11.7 30.0 34.4 58.8 21 .o 33.2 30.5 58.1 24.3 33.0 30.9 54.5 18.5 31.5 30.7 57.0 21.1 31.6 20.3 55.8 6.3 28.6 22.3 56.4 .7 30.5

34.5 57.2 25.8 31.7 28.1 55.4 15.9 30.5 33.0 56.4 21.2 31.5 37.1 60.6 26.4 34.3 32.1 55.7 18.1 30.4 34.3 57.3 22.0 30.3 17.4 55.4 -4.4 30.5 32.7 57.9 20.8 32.7 34.6 58.3 25.3 32.1 31 .O 58.6 17.4 34.3 (con.) Table 20.-(con.)

Average Daily Maximum and Minimum Temperatures Year an. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. ~nnual

Max. 34.7 58.2 Min. 24.4 35.5 28.4 56.6 14.1 32.2 25.8 56.0 11.2 30.4 33.5 58.2 18.8 31.9 35.8 57.0 16.3 30.9 33.5 56.5 20.8 31.7 29.8 56.8 14.3 32.7 31.8 54.3 16.6 31.1 19.9 56.4 -2.2 29.0 18.2 54.2 -.8 30.6

31.9 55.3 17.8 30.2 29.7 57.7 17.2 30.8 39.5 57.7 30.2 33.9 30.2 55.0 17.2 32.1 31.2 52.8 21.8 29.8 32.2 55.5 20.2 31.6 22.6 55.8 5.1 31.2 33.9 59.3 25.6 34.6 32.9 54.5 19.7 31.7 27.1 55.5 13.8 31.1

34.0 57.3 21.8 32.9 28.1 56.0 12.1 32.1 26.5 57.3 12.7 33.2 33.3 54.6 23.8 31.3 32.7 56.2 25.1 32.3 32.3 57.0 23.4 33.6 34.5 57.5 25.3 32.9 31.O 54.8 18.9 32.1 23.7 55.1 12.3 32.2 28.4 55.5 18.4 32.1 (con.) Table 20.-(con.)

Average Daily Maximum and Minimum Temperatures Year Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Annual

50-year average 1931-80 30.1 17.5

llncludes corrections of confirmed errors in published climatological data.

Table 22.-Daily minimum temperature statistics as in table 21 MINIMUM DAILY TEHPERATURE I'Efifi! STAIIUAHT! LIEVIATIOll r AldD EXTREMF VALUES

1931-1977 EXCEPT PS NOTtD

JAL I JAN 1 JA'd 11 JAh 11 JAP\' 21 JAk 21 FEH 1 FER 1 FE9 11 FER 11 FE13 21 FEB 21 '147 1 MAR 1 iVI A 'i 1 1 NAR 11 "IAK 21 HAR 21 API< 3 APR 1 APY 11 APR 11 Ap14 21 APR 21 Jlr\l 1 MPY 1 .lay 11 MAY 11 "IAY 21 HAY 21 JUfd 1 JUN 1 JUll 13 JUN 11 JUI~I21 JbIU 21 JLlL 1 JUL 1 JUL 11 JUL 11 JUL 21 JUL 21 AuG 1 AUG 1 AlIG 11 AUG 11 AIJG 21 AUG 21 SEP 1 SEP 1 SEP 11 SEP 11 StP 21 SEP 21 OCT I CCT 1 OCT 11 OCT 11 OCT 21 OCT 21 >")\I 3 luov 1 rdov 11 luov 11 'JDd 21 [uov 21 'IEC 1 OEC 1 r)EC 11 DEC 11 DEC 21 DEC 21

JAN J API FEi3 FER IVI AR MAR APY npq Pi A Y MAY J LJril Jurl JUL JUL A(JG PUG SEP SEP OCT OCT r\l G v NO V DEC DEC Table 23.-Mean temperature statistics as in table 21; based on arithmetic average of daily maximum and minimum temperatures

MEAN DAILY TEMPERATURE YEAN- STANDARC DEVIATION, AN0 EXTREME VALUES

STI\T1311 r,(juF'F r) 1073fjb PKIEST IiIVEK EYP FOR (COIIT~OL STP, 1931-1977 EXCFPT AS NOTED

10-CAY AIVD PtONTHLY EXTREME DAILY VALUES

I'ER I OL STU. MEDIAN 1912-1982 AVG. STD. MEDIAN PERIOD 9EiIPi? PIGH LOKqYR LOW DEV. LOW BF-GIluS

JAX .L 14.1 JAN 1 JAIJ 11 12.0 JAN 11 Jc,i,: 23 11.1 JAK 21 FEP 1 15.0 FED 1 Ft:13 11 19.9 FEB 11 FCO 21 23.3 FEB 21 r.: r.: A 1 23.1 MAR 1 rf*A>? 11 26.9 YAR 11 1AR 21 30.0 MA2 21 APH 1 34.6 APR 1 Aijri 11 37.1 APP I1 APli 21 39.5 APR 21 {YAY 1 42.5 MAY 1 VAY 11 't4.2 MAY 11 'YAY 21 lth.9 MAY 21 JLJ~J i 50.4 JUN 1 JUr! 11 51.2 JLJN 11 JUN 21 52.1 JUN 21 J'.JL 1 55.5 JUL 1 JLIL 11 58.1 JUL 11 JUL 21 58.2 JUL 21 AlJG i 58.2 AUG 1 Allf 13 57.4 AUG 11 A(!G 21 53.7 AUG 21 SEP 1 51.6 SEP 1 SEP 11 46.9 SEP 11 SEP 21 46.0 SEP 21 OCT 1 41.3 OCT 1 OCT 11 38.3 OCT 11 ClCT 21 32.9 OCT 21 .!aV 1 28.9 nov I r4ov 11 25.6 NOV 11 ldOV 2; 22.4 NOV 21 UEC I 19.5 GEC 1 UEC 11 18.0 DtC 11 IIEC 21 15.9 OEC 21

PiONTH MONTH

JAN 4.9 JAU FEH 11.8 FEB I"-$ A H 20.9 V AR APR 33.5 APR '4 AY 40.8 MAY JUN 47.9 JUN J iJ L 54.0 JUL AUG 52.8 AUG SEP 43.5 SEP OC T 32.4 OCT nlov 19.9 NOV DEC 10.9 DEC Table 24.-Frequency distribution of daily maximum temperatures at Priest River Experimental Forest control station; based on years 1931-77 and 24-hour period ending at 5 p.m. P.s.t.

MAXIMUM DAILY TEMPERATURE PEHCEf TAG€ FREQUENCY DISTRIBUTION OF nAILY VALUES -GIVEN TO TEVTHS PEHCEMTv DECIMAL POIVT OMITTED

TF NPEdrll LIR~HGb LF 2 pcl 3~ 35 41- 45 50 55 60 65 70 75 80 85 90 95 100 VFLl. Tn T3 TO TO TO TI: TO TO TO T'S TO TO TO TO Tn TO Ah0 PRD. Ll E G I I\IS 2~ 29 34 39 44 49 54 59 64 69 74 79 84 89 911 99AROVF BEGINS

JAIil 1 JAN 1 JAl" 11 JAN 11 JAr' 31 JAN 21 FEH 1 FEB 1 FEL4 11 FE3 11 FED 71 FEH 21 '?AH 1 MAR 1 WAR I1 PIAR 11 NAI, ?I VAQ 21 APq I llPR 1 APtl 11 APH 11 APR 21 APY 21 NAY 1 MAY 1 Pl A y 1 1 "IY 11 MAY 21 MAY 21 JIJld 1 JUrJ 1 JUr4 11 JUN 11 JUIC 21 JUN 21 JclL 1 JUL 1 JUL 11 JLlL 11 JUL 71 JUL 21 AL!G 1 AUG 1 AUG 11 AUG 11 nur. 21 AUG 21 SEP 1 SEP 1 SLP 11 SEP 11 SEp 71 SEP 21 OCT 1 OCT 1 OCT 11 OCT 11 OCT 21 OCT 21 VOV I NOV 1 hOV 11 NOV 11 (IOU 21 NOV 21 DEC 1 DEC 1 UEC 11 DEC 11 DEC 21 DEC 21 tY0NTtI

JAN JAN FEB FEB YAR MAR APR APR MAY MAY JUlJ JUFJ JUL JUL AUG AUG SEP SEP OCT OCT ll0V JEC , Table 25.-Frequency distribution of daily minimum temperatures as in table 24

MINIMUN DAILY TEMPERATURE PCHCEI'TAGE FREQLIENCY DISTRIBLITION OF DAILY VALUES -GIVLN TO TErdThS PERCENT* CIECIMAL POINT OMITTED

1073Rb PRIEST KlVEH EXP FOh

PHU. YEiIrrr

JAN 1 JAN 1 JAN 11 JAN 11 JAk 21 JAW1 FEE 1 FEd 1 FES 31 FEB 11 FEL, 21 FEB 21 I 1 WQR I (YAW 11 MAR 11 IIAR 21 WAR 21 APP I PPR 1 APt? 11 APH 11 AP9 21 APQ 21 MAY 1 MAY 1 niny 11 NAY 11 '?UY 21 MAY 21 JUrr 1 JUh 1 JUPd 11 JUNJUV 2111 JJhI 21 JUL 1 JUL 1 JUL 11 JUL 11 JUL 21 JUL 21 u 1 AUG 1 ALJG 11 AUG 11 AUG 21 PUS 21 SEP 1 SEP 1 SEP 11 SEP 11 SEP 21 SEP 21 OCT 1 OCT 1 nCT 11 OCT 11 OCT 21 CCT 21 rJOV 1 NOV 1 'lo\, 11 rcov 11 IJOV 21 NOV 21 3EC I OEC 1 OEC 11 OEC 11 9EC 21 DEC 21

MONTI

J Art! JAN FEH FEB "IAH MAR IPS APR 14AY MAY JU~J J Uhl JUL JUL AUG AUG SEP SEP OC T OCT h! 0 v NOV DEC DEC Table 26.-Dry bulb temperature (OF) observed at 3 p.m. P.s.t. at fire-weather stations in Priest River Experimental Forest. Data are for complete 20 years, 1951-70, at clearcut station; for indicated numbers of years at Gisborne Lookout

DRY BULB TEMPERATURE VEPY, STANDARD OEVIATIONv AND EXTREME VALUES

STATION hLlr:PEP 1011205 PRIEST IIIV€II EXP FOh (CLtARCUT) 1951-1970

10-UAY AND MONTHLY EXTREME DAILY VALUES

PEHIOrr HIGHEST STD. MEDIAN AVG. PERIOD YCGIhlS AVC YP OEV. HIGH LOG DEV. BEGINS

PIAY 1 73.1 66 71.5 97.8 6.0 MAY 1 YAY 11 72.3 58 78.5 48.9 6.1 IYAY 11 I'IAY 21 78.9 58 79.5 51.2 6.4 MAY 21 JiJN 3 00.4 69 ei.0 56.0 7.3 Jbli 1 JUiu 11 03.1 61 92.0 57.6 6.0 July 11 JbU 21 74.0 70 el. 0 55.9 &.A dm 21 JUL 1 80.9 60 88.0 62.2 P.5 JUL 1 JUL 11 92.4 6U 92.0 68.8 7.0 JUL 11 JiJL 21 R7.7 60 91.0 68.9 8.5 JClL 21 AUG 1 88.7 61 91.5 67.6 7.7 Ad6 1 AUG 11 95.8 67 90.5 69.1 9.7 AUG 11 AL'G 71 86.5 70 86.5 60.4 7.2 AclG 21 SEP 1 P5.4 63 e4.0 61.1 8.8 SEP 1 SEP 11 78.3 56 e3.5 53.9 5.5 SEP 11 SEP 21 79.5 52 76.0 52.7 E .9 SEP 21 OCT 1 69.1 52 73.0 47.2 5.5 OCT 1 OCT 11 64.5 63 66.5 44.7 4.1 3CT 11 OCT 21 59.1 65 57.5 40.3 6.2 OCT 21

PlOiiTtl PIONTH

P'I A Y 74.2 58 82.5 44.5 4.0 WAY JUrJ 78.8 61 87.0 51.0 3.5 JUFI JcrL 87.7 60 93.5 50.8 6.0 JLJL AUG P8.2 67 94.0 57.0 5.4 AUG SEP 70.9 67 86.5 49.3 4.0 SEP OC T 55.4 53 73.0 38.6 4.7 OCT

DRY BULB TEMPERATURE h~prd, STANDARD DEVIATION, A1',IO EXTREME VALUES

10-CAY AND PICNTHLY EXTRENE DAILY VALIJES

1 LOhLST I AVG. STD. P'EDIAN AVG. STU. MEPIAN PERIOD AVbrY'? I HIGHrYR hIGH DEV. HIGk LOWqYS LOW DEV. Lek4 BEGINS J .JUL 1 52.e 5F I !{S bu 76.0 4.4 76.0 39 66 48.6 6.6 49.0 JUL 1 JLlL 11 6O.U 68 I l?7 70 70.7 4.9 79.0 45 57 56.0 6.7 55.5 JUL 11 JI.IL 21 59.570 I 8659 78.2 4.0 79.0 38 54 55.7 9.6 55.0 JSL 21 A I \ 1 57.0 62 1 53 hl 79.3 5.3 80.0 40 56 541 7.8 54.5 AlJG 1 AUS 11 32.bfthe 1 t7 €7 77.4 4.d 76.5 41 64 55.7 9.5 55.5 AUG 11 AliG 21 46.Uk6fl I fl7 6P 76.9 11.0 80.5 38 60 50.9 8.6 52.0 ALJG 21

I JUL nh.P* 3.3 74.b 6U 61.G 55 I ?7 70 A1.4 3.5 82.0 38 54 46.1 4.7 46.0 JUL WJG t.6.24 4.5 75.0 67 57.~6q I 93 61 2. 4.4 62.0 38 60 47.0 5.8 4'5.5 n UG 65. ;5F Table 27.-Relative humidity (percent) observed at 3 p.m. P.s.t. as in table 26

RELATIVE HUMIDITY MEAN* STANDARD DEVIATIONt AND EXTREME VALUES

STATIOK tbUrlFER 100205 PRIEST RIVEK EXP FOR (CLFARCUT)

10-DAY AND MOIdTHLY PERIOD MEANS 10-DAY AND NONTHLY EXTREMES

PRD. STD. HIGHEST LOWEST AVG. STD. NEDIAM AVG. STO. MEDIAN PRO. HEGINS DEV. MEUIAN AV'UqYR AVG t YH HIGH DEV. HIGH LOW DEV. LOW BEGINS hAY 1 12.1 44.5 72.8 61 27.6 66 76.8 24.4 RAY 1 AAY I1 9.6 41.0 57.1 60 27.7 64 77.7 20.7 MAY 11 viAY 21 7.3 42.5 61.5 53 37.2 63 P0.4 22.2 PiAY 21 JUN 1 10.3 45.0 62.4 53 22.2 65 74.9 23.9 JUN 1 JUN 11 9.5 42.0 61.3 70 29.4 69 73.9 25.1 JUN 11 JUN 21 11.4 39.5 69.6 69 27.1 62 76.3 24.1 JUN 21 JUL I 8.5 39.0 52.0 69 22.R 68 68.6 22.E! JUL 1 JUL 11 6.9 33.5 43.0 56 21.0 60 55.6 21.0 JUL 11 JUL 21 7.1 27.0 46.5 55 19.4 56 56.2 17.7 JUL 21 AClG 1 9.1 28.5 51.6 62 20.4 59 62.1 17.0 AUG 1 AUG 11 10.1 27.5 57.3 68 12.9 67 55.0 16.5 AUG 11 AUG 21 12.9 35.5 61.5 54 20.5 67 68.6 20.7 AUG 21 SEP 1 9.3 34.5 53.4 70 22.4 67 66.0 20.1 SEP 1 SEP 11 13.1 40.0 71.0 59 27.1 51 75.3 21.8 SEP 11 SEP 21 12.3 46.0 69.0 59 20.5 67 77.6 25.9 SEP 21 OCT 1 12.6 55.0 87.8 51 36.3 66 68.1 30.8 OCT 1 OCT 11 13.0 56.0 89.4 51 33.6 69 86.8 37.5 OCT 11 r)CT 21 9.7 72.0 90.6 51 48.3 65 53.0 45.4 OCT 21

,-1ONTti MONTH

MAY 6 1 43.5 56.6 61 34.6 58 89.8 17.9 MAY JUN 5.4 44.0 57.4 53 34.5 60 90.1 19.3 JUN dIIL 4.7 33.0 43.7 55 33.9 60 80.5 17.0 JUL AUG 8.0 31.5 47.1 64 19.5 67 82.8 14.1 AUG SEP 7. A 40.5 60.8 59 2'4.q 67 89.9 17.2 SEP OCT 9.6 58.5 89.3 51 50.3 hb 96.0 28.8 OCT

RELATIVE HUMIUITY PIEARI. STANDARD DEVIATION. AND EXTREME VALUES

STATIOIU NIJI'UER 100202 GTSUORht LOOKOUT

AVG. STD. MEDIAN AVG. STD. MECIAN HIGH OEV. HIGH LOWtYR LOW DEV. LOW I JlJL 1 19 53.3 11.1 53.0 72.4855 31.5 te I 180 66 JUL 1 JUL 11 20 95.6 9.7 46.0 h2.0 57 24.4 b0 I 100 65 JUL 11 JllL 21 20 't2.0 10.9 40.5 70.3 55 28.5 51 I 100 70 JUL 21 AlJG 1 20 46.5 13.6 43.5 76.9 57 28.9 67 I 100 64 AUG 1 At16 11 29 44.6 13.C' 43.0 h7.5#bd 16.h 67 I 1GD 6C AUG 11 AUG 21 12 47.5 16.4 45.5 75.0160 16.5 70 I 100 64 AUG 21 53.02

MONTH

# IPdCLUDES ESTIPIATC FOR CAYS WITh YISSING LATn * VAL.CIE DEb'I\/Fl. FROPI THE THREE 10-UAY MEANS 2 PRECEOIrIG U4LUE AUJUSTFD TO COriPLETL 20-YH PEHIOU Table 28.-Frequency distribution of dry bulb temperatures (OF) observed at 3 p.m. P.s.t.

DRY BULB TEMPERATURE PERCE:lTAGE FREQUENCY DISTRIBUTION OF DAILY VALL1ES -GIVtb' TO TENTHS PERCENT, DECIMAL POINT OMITTED

STATIOFI NUMOEH 100205 PHIEST RlVER LXP FOR (CLEARCUT) 1951-1970

PRD. BEGINS hAY 1 MAY 1 YAY I! MAY 11 I'nAY 21 NAY 21 JUR I JUN 1 JllN 11 JUk 11 JUIII 21 JUN 21 JUL 1 dUL 1 JlJL 11 JUL 11 J'IL 21 JUL 21 A 1 AUG 1 AUl3 11 ALIG 11 AUC- 21 fiUG 21 SEP 1 SEP 1 SEP 11 SEP 11 SLP 21 SEP 21 3CT 1 OCT 1 OCT 11 OCT 11 C'CT 21 UCT 21

KONTH

,.lAY (IAy JUWE JUIJ JUL JllL All(; AUG 2EP SEP OCT oc T

DRY BULB TEMPERATURE PERCEI TkGE FREQUEhCY IJISTPIBUTIOI'J OF DAILY VALCES -6IVIN TI) TEIITHS PERCERiT, DECIMAL POIPIT OMITTEC

STPT ION NUNUER

TEI~'PERETURE RANGE 3 it 5 50 55 60 65 70 75 9n 95 100 PrTd . Ti' Tn TO Ah0 PRD. ~CGII,IL I 94 99 ABOVE BEGIkS

Jcll. 1 JUL 1 JUL 11 JlJL 11 J~JL 31 dUL 21 A'J; 1 AUG 1 AlJG 11 AUG 11 A'lG 21 (12 YISI ACG 21

J LJ L 9 PUG Table 29.-Frequency distribution of relative humidity (percent) observed at 3 p.m. P.s.t.

RELATIVE HUMIUITY

90 95 100 l't'r~ , TO TI; PRO. ,5f L7Ilr' 91, 99 HEGIIus

V4Y I MAY 1 MAY 11 MAY 11 'VAy 21 MAY 21 JUN 1 JUN 1 JUrJ 11 JUh 11 JUPl 21 JUY 21 JUL 1 JUL 11 JUL 111 JUL 21 JUL 21 AlJG 1 AUG 1 AUG 11 AUG 11 AlJG 21 AU6 21 SEp 1 SEP 1 SEP 11 SEP 11 SEP 21 SEP 21 OCT 1 OCT 1 C)CT 11 OCT 11 OCT 21 OCT 21

1~10NTt~ NONTH

MAY MAY JLJN JUN JUL JUL ALJG AUG SEP SEP OCT OCT

PFHCE .TAGE FuEfluEhCY DISTRIBUTION OF UAILY VALUES -GIVEIJ TO TEhiTHS PFRCEhlT+ OECIPAL POIiJT OMITTED

PRD. BEGINS

32 dUL 1 5 JUL11 36 JUL 21 40 AuG 1 20 AUG 11 45 AUG 21

2 5 JUL 3 4 AUG Table 30.-Frequency distribution of three-way combinations of dry bulb temperature (OF), relative humidity (percent), and windspeed (milh) at 3 p.m. P.s.t.

TEP~PERATURE- XELATIVE HLNIUITY - k;~rdosp~co PERCEYTAGE FREIUEUCY OF OCCL'RREfdCE FCH SELECTCU COMBINATIONS -GIVEN TO TENTHS PEhCENT, CECIMAL POINT OHITTEn

STATION hUFFEti 100205 PRIFST RIVER LXP F04 (CLFAPCUTI MOKTH MAY--- WING SPEED 0-4 PPH I WIND SPEELI 5-9 MPH I WIND SPFEO 10-14 MPH I I PELATIVE HUMIOITY I HELATIVE HUMIDITY I RELcTIVE HUNIDITY 1 11 21 31 41 51 61 71 81 91 I 1 11 21 31 41 51 61 71 81 91 1 1 11 21 31 41 51 hl 71 81 91 TEMP. TO TO 70 TO TO TO TO TO TO TO 1 TO TO TO TO TO TO TO TO TO TO 1 TO TO TO TO TO TO TO TO TU TO DEGF 10 20 30 40 50 60 70 80 90 100 1 10 20 30 40 50 60 70 80 9IllOO I 10 20 30 40 50 60 70 80 90 lo0 ------1------1------Clop I I 95-99 1 I 90-9'1 2 I I 85-89 2 7 I 3 I 80-84 12 25 7 2 I 8 8 I 75-73 13 35 12 2 I 1518 8 2 I 70-74 10 45 30 8 2 I 3 28 30 5 I 65-69 10 25 28 13 15 T 5 20 12 15 3 2 2 I 60-64 2 8 18 17 8 10 5 I 2 15 17 5 7 22 1 55-59 8 10 22 22 13 13 5 21 8 8 810 2 3 I 2 50-54 7 22 25 20 15 18 7 I 2 712 7 3 2 2 21 2 95-49 2 2 2 7101812 81 2 3 2 L 5 21 40-44 3 7 A1 2 2 I 2 35-39 2 21 I 30-34 I 1 3 0 I I ------1------1------TOTAL 2 48 154 113 86 75 53 55 43 27 I 35 101 83 50 28 8 8 12 3 I 2 3 2 3 I I NUMBER 129 93 68 52 q5 32 33 26 161 0 21 61 50 30 17 5 5 7 21 0 0 1 2 0 1 2 0 u 0

MOhTH JUN--- WIND SPEED 0-4 MPH I WIND SPEED 5-9 MPH I MIND SPEED 10-14 MPH I I RELATIVE HUMIDITY I RELATIVE HUMIDITY I RELATIVE HUMIDITY 1 11 21 31 41 51 61 71 81 91 1 1 11 21 31 41 51 61 71 81 91 I 1 11 7' 31 41 51 61 71 81 91 TEMP. TO TO TO TO TO TO TO TO TO TO 1 TO TO TO TO TO TO TO TO TO TO I TO TO I TO TO TO TO TO Tu TO DEGF 10 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 90 100 I 10 30 40 50 60 70 80 9U 100 ------1------1------Cl00 I I 95-99 I I 90-94 7 3 I 3 I 85-89 9 31 19 2 I 3 9 5 I 80-84 5 26 29 3 I 2 2 19 12 2 I 75-79 10 48 46 9 2 1 2 26 26 3 I 70-74 3 26 51 19 3 9 I 3 22 17 17 5 I 65-69 10 36 29 22 5 3 I 3 21 12 5 I 60-64 2 I0 21 26 21 14 7 I 2 7 26 12 10 3 I 55-59 3 5 9 21 15 91 3 2323 I 50-54 2 3 7 327 91 323 I 45-49 3 2 31 2 3 I 40-44 I I 35-39 I I 30-34 I I 30 I I ------1------1------TOTAL 27 149 195 87 62 50 44 51 21 I 2 10 89 91 63 26 19 5 7 I 5 2 2 I I NUMBER 0 16 87 114 51 36 29 26 30 12 I 1 6 49 53 37 15 11 3 4 0 I 0 0 3 1 0 1 0 0 u 0 Table 30.-(con.)

TEPPERATURE - RELATIVE HUMIDITY - WINDSPEEO PERCENTAGE FREQUENCY OF OCCURRENCE FOR SELECTED COMBINATIONS -GIVEN TO TENTHS PERCENT, DECIMAL POINT OMITTED

STATION NUNREH 100205 PRIEST RIVER EXP FOH- ICLI-ARCUT) 1951-1970 MOilTH JUL--- NIRD SPEED 0-4 MPH I hIND SPEEL 5-9 MPH I WINO SPEED 10-14 MPH

ClOO 2 95-99 3 25 90-94 53 17 2 85-89 51 60 7 80-84 27 91 25 3 2 75-79 12 61 25 10 3 70-74 3 27 28 22 10 5 2 65-69 3 5 15 20 10 10 60-64 3 7 13 12 5 55-59 2773 50-54 2 45-49 40-44 35-39 30-34 3 0 Table 30.-(con.)

TEMPERATURE - RELATIVE HUMIDITY - WINDSPEED PERCENTAGE FREQUENCY OF OCCURRENCE FOR SELECTED COMBINATIONS -GIVEN TO TENTHS PERCENT3 DECIMAL POINT OMITTED

STATION NUMBER 100205 PRIEST RIVER EXP FOR (CLEARCUT) MONTH SEP--- WIND SPEED 0-4 MPH I WIND SPEED 5-9 MPH I WIND SPEED 10-14 UPH I I RELATIVE HUMIDITY I RELATIVE HUMIDITY I RELATIVE HUMIDITY 1 11 21 31 41 51 61 71 81 91 I 1 11 21 31 41 51 61 71 81 91 I 1 11 21 31 41 51 61 71 81 91 TEMP. TO TO TO TO TO TO TO TO TO TO I TO TO TO TO TO TO TO TO TO TO I TO TO TO TO TO TO TO TO T? TO DEG F 10 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 9U 100 ------1------1------C100 I I 95.99 I I 90-94 10 3 I 5 I 85-89 23 31 2 I 9 3 1 80-84 17 73 26 3 2 I 9 12 I 75-79 7 75 35 2 2 I 2 14 10 I 70-74 2 7 45 40 21 2 I 3 14 10 I 65-69 23 23 36 12 5 2 2 I 2979 I 60-64 9283124 9 7 5 I 53553 I 55-59 5 7 14 17 14 21 9 9 I 25275 3 I 50-54 2 2 7 3 5 7 919161 2 32 1 45-49 2 2 9 3 51 I 40-44 I 2 I 35-39 I I 30-34 I I 30 I I ------1------1------TOTAL 2 66 265 168 111 64 36 47 38 29 I 29 61 36 16 14 9 3 5 1

WIND SPEED 0-4 MPH I MIND SPEED 5-9 MPH I WIND SPEED 10-14 RPH I RELATIVE HUMIDITY I RELATIVE HUUIDITY I RELATIVE HUMIDITY 11 21 31 41 51 61 71 81 91 I 1 11 21 31 41 51 61 71 81 91 1 1 11 21 31 41 51 61 71 85 91 TEMP. TO TO TO TO TO TO TO TO TO I TO TO TO TO TO TO TO TO TO TO I TO TO TO TO TO TO TO TO Tu TO DEG F 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 90 100 ------1------1------ClOO I I 95-99 I I 90-94 I I 85-89 I I 80-84 I I 75-79 2 13 6 I 2 I 70-74 2 13 19 11 2 I 4 6 I 65-69 9 26 32 4 4 I 2 2 I 60-64 6241728 9 6 2 I 2 2 2 I 55-59 9 35 37 22 22 15 6 7 I 7 4 6 I 50-54 2 13 20 32 35 32 39 19 I 9447 2 21 45-49 2 6 9 22 33 43 30 35 I 2 4 2 4 I 40-44 4 11 17 19 33 1 222 4 I 2 35-39 2 6 2 19 301 2 I 30-34 6 61 I 3 0 I 2 I ------1------1------TOTAL 4 54 128 126 113 122 113 119 130 I 9 22 13 17 11 4 4 9 I 2 I I NUMBER 0 229696861666164701 0 0 512 7 9 6 2 2 51 0 0 0 0 0 0 1 0 U 0 Table 30.-(con.)

TEPPLRATURE - RELATIVE HbMIDITY - WINDSPEED PERCENTAGE FHEQUE84CY OF OCCURRENCE FOR SELECTED COMBINATIONS -GIVEPI TO TEtITHS PERCENT, DECIMAL POINT OMITTED

STI\TIOIU NUMBER 100202 GISBOHNE LO 1951-1970 MO(ITt$ ---JUL WIYU SPEED 0-4 MPH I WINO SPEED 5-9 MPH I WIND SPEED 10-14 MPH 1 I RELATIVE HLIMIUITY I RELATIVE HUMIDITY I RELATIVE HUMIDITY 1 11 21 31 41 51 61 71 81 91 I 1 11 2L 31 41 51 61 71 81 91 I 1 11 21 31 41 51 61 71 81 91 TEMP. 10 TO TO TO TO TO TO TO TO TO I TO TO TO TO TO TO TO TO TO TO I TO TO TO TO TO TO TO TO TO TO DEG F 10 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 90 100 1 10 20 30 40 50 60 70 80 9U 100 ------1------1------Cl00 I I 95-99 I I 90-94 I I 85-89 3 2 I 3 I 80-84 3 15 5 I 12 15 3 I 5 3 75-79 2 21 21 5 3 I 7 36 31 8 I 15 12 2 70-74 13 21 10 7 3 I 13 67 33 8 I 7 18 13 3 65-63 2 18 28 5 5 I 5 23 31 12 2 I 321 8 3 3 60-64 28155532 I 8 21 15 5 2 I 7 12 12 3 55-59 8753 I 53157107 I 2 8 212 3 50-54 235531 283571 2 3575 45-49 2 2 71 5 71 2 8 40-44 2 T 2 5 1 2 35-39 2 1 I 3 30-34 I I 3 0 I I ------1------I------TOTAL 8 54 74 59 30 23 13 13 12 I 7 69 150 100 51 21 16 16 18 I 30 63 44 20 21 10 7 18 1 I NUMBER 0 5 33 45 36 Id 14 8 8 7 I 0 4 42 91 61 31 13 10 10 11 I 0 O 18 38 27 12 13 6 4 11

MONTH AL--- WIhD SPEED 0-4 MPH I WINO SPEED 5-9 "PI1 I WIND SPEED 10-14 MPH 1 kELATIVE HWIIDITY I RELATIVE hUYIOITY I RELATIVE HUI'IIOITY 1 11 21 31 41 51 61 71 81 91 I 1 11 21 31 41 51 61 71 81 91 I 1 11 21 31 41 51 61 71 81 91 TEMP. TO TO TO TO Tq TO TO TO TO TO I 10 TO TO TO TO TO TO TO TO TO I TO TO TO TO TO TO TO TO TU TO DEGF 10 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 90 100 I 10 20 30 40 50 60 70 80 90100 ------1------1------El00 I I 95-99 I I 90-94 2 I I 85-89 6 6 I282 I2 4 80-84 6 15 I 2 13 13 6 I22 4 75-79 2 19 13 2 I 2 84417 4 I 4 15 2 2 70-74 21021 b 4 6 1 4 21 48 21 8 2 I 2 10 29 6 4 65-69 417111 2 4 2 I? 13 42 44 D 4 I 2 6 15 4 b0-64 2 17 15 4 4 I 2 10 29 13 8 6 2 I 810 6 6 2 55-59 44266 I 22101282 I 4266 2 50-54 2 2 6 61 4 2 4 61 2 b242 45-49 4 6 1 2 2 4 4131 2 6 40-44 6 1 2 13 I 2 35-39 I 't I 30-34 I I 5 0 I I ------r------r------TOTAL 17 54 54 3P 23 21 13 12 17 I A 35 94 125 100 40 31 19 13 36 I 4 10 29 48 38 15 17 10 6 12 Table 31.-Daily maximum temperature (OF) at fire-weather stations in Priest River Experimental Forest; statistics based on 24-hour period ending at 3 p.m. P.s.t. Data are for complete 20 years, 1951-70, at clearcut station; for indicated numbers of years at Gisborne Lookout

PIEAN, STANDARD DEVIATION* AND EXTREME VALUES

1951-1970

10-DAYANU MONTHLY EXTREME DAILY VALUES

STL . LI\IC,. STU. WEDIAN AVG. STD. MEDIAN PERIOD ncv. 1-1 I G H OEV. HIGH LOWvYR LOU DEV. BEGINS

5.q 74.0 52.2 6.7 MAY 1 q.7 79.7 54.8 5.9 KAY 11 5.9 tjn.1 59.7 7.1 MAY 21 5.6 d?. 2 62.9 6.9 JUN 1 5.7 83.7 63.9 5.8 JU~11 'i .0 h3.H 63.0 4.7 JUk 21 (4 .t3 89.5 68.3 6.7 JUL 1 t.9 92.5 74.7 6.3 JUL 11 9.3 92.4 76.0 6.8 JUL 21 =I .2 52.6 75.1 6.9 AUG 1 6 .1 51.4 73.8 10.1 AlJG 11 7.1 04.6 67.9 8.6 AOG ill 5.9 f6.3 67.6 8.1 SEF 1 6, .5 E 4. 2 60.4 6.2 SEP 11 7 .b 72.1 56.5 7.5 SEP 21 f1 .7 74.6 5 7.8 ClCT 1 5.7 66.5 49.8 4.7 OCT 11 5.4 61.0 43.5 5.7 OCT 21

iY 0 N T ti

z. 9 C.2.9 49.8 4.3 MAY 3 .5 67.4 58.7 4.7 JUk 3.0 74.7 66.9 6.1 JLIL t, .0 95.4 66.1 8.4 AUG 4.4 ee.0 55.3 3.7 SEp 'I .4 75.1 42.2 4.5 OC T

MAXIMUM DAILY TEMPERATURE WEAN* STANDAFrl DEVIATION* P.PJ@ EXTREME VALUFS

1951-1970

10-PAY AND MONTHLY EXTREPE DAILY VALllES

AVG. STD. MEDIAN FERIOD LOW DEV. LOW BEGINS

JUL 1 la t7.tL 5.6 68.'-? 77.5 68 56.rH55 JUL 1 JuL 11 19 72.4 4.8 72.0 62.1 60 64.5 63 JUL 11 JVL 71 20 73.1 4.7 72.11 Bl.1 62 65.7 70 JUL 21 AUG I 19 72.1 5.1 72.0 81.5 61 61.5 b4 AUG 1 All= 11 19 72.3 6.4 71.0 ati.0 67 57.'>116;1 ALG 11 ALJG 21 12 69.4 7.b 60.0 80.1 70 51.G1160 AlJG 21 66. id

MONTH

JUL PUG

tf IhCLCIDES TSTlIIATE FOP DAYS hITti PIISSING UATA 4 VALUE DFdI\/FL F&OI"I IHE TUt

MIPlIMUM L:AILY TEMPERATURE PEAN. STANCARL C)EVIATIOMr AN0 EXTREME VALUES

STATION I\IUI"lI'ER 105205 FRIES1 HIVEIt CXP FOh (CI-EARCUT) 1951-1970

10-lrAY Alil; ?lr)NTIlLY PERIOL! I~FAI4S I 10-lJirY AF!U WONTHLY EXTREhF SAILY VALUES I PEfiIOn ST[. HILHLST LOWEST I AV6. STD. MEDIAh AVG. STO. PEOIuN PERIOD YEGINS \"EA?l s1t.V. 14EUIfl*hl AVL-qYt( AVbrYR 1 ttIGH,YR tIIGH DEV. HIGH LOWrYR LOW IIEV. LOW BEGINS

MAY I FiAY 1 VAY 11 MAY 11 MAY 21 MAY 21 JClN 1 JUPJ 1 JUN 11 JUh 11 JLJI~I21 Jurd 21 JUL 1 JUL 1 J ?I L 1I. JUL 11 JUL 2?. JUL 21 AUG 1 AUG 1 AYG 11 AUb 11 AUG 21 AUG 21 SEP 1 SEP 1 SEP 11 SEP 11 SEP 21 SEP 21 OCT 1 OCT 1 OCT 11 OCT 11 OCT 21 OCT 21.

MONTH I I lVlA Y 36.1 2.0 35.0 40.257 33.155 I 5366 4e.8 3.1 49.0 16 54 24.9 3.7 24.5 MAY JUN 42.2 2.3 41 46.3 69 38.6 60 I 60 70 54.6 3.1 53.5 27 56 31.0 2.3 32.0 J U Id JUL 43.5 1.e 43.0 47.755 40.855 I 6355 55.9 5.0 55.0 30 62 33.0 1.5 31.0 JLIL 4UG 41.5 2.5 41.11 46.4 65 36.5 55 I 60 65 F:4.h 3.5 55.5 27 69 31.1 2.7 31.0 PUS SEP 36.3 2.7 35.0 40.6 5'3 32.9 60 1 60 67 50.2 3.6 50.0 18 57 24.1 3.4 23.5 SEP '3 C T 51.4 2.5 31.0 35.251 26.b52 I 5167 45.6 3.3 45.0 15 70 19.t) 3.1 20.0 OCT

MINIMUM DAILY TEMPERATURE FIEAV, STAFIDAHG DEVIATIONr AND EXTREME VALUES

STATION NUPHtH 100202 GISPORNF LOCKOUT 1951-1970

10-3AY ANU MONTHLY PERIOD MEANS 10-L'AY AND PChITt'LY EXTREiYE GAILY VALUES

PERIOli NUPI. STLI. HIGhEST LOhkST AVG. STD. MEDIAN PEP 1011 DEGINS YRS ILEA\ DEV. ?IELIIAIJ AVGrYk AVbqYR LOW flE\I. LOk EEGIb'S

JUL 1 18 47.8 4.5 47.0 58.3 66 40.Un55 37.9 JUL 1 JbL 11 19 50.7 9.6 49.5 62.1 60 44.2 68 42.0 JUL 11 JtJL 21 20 51.3 3.9 51.0 58.2 60 44.7 70 40.9 AUb 1 19 50.6 4 50.L 58.0 65 43.9 56 41.3 JULBUG 211 AUG 11 19 50.5 5.5 49.0 65.9 67 43.3 bh 42.3 AUG 11 AUG 21 12 47.6 5.5 47.0 55.4 7F 37.0860 38.5 AlJG 21 46.34

YONTH MONTH

JUL 50.0* 2.0 57.0 60 46.6855 36 5 JUL AUG 49.5* 5.8 58.1 67 43.5t64 37.6 p Ur, 49.02

# IIuCLUUES ESTIVATE FOR GAYS WITH YISSING OATA * VALUE DERIVED FROM THE THREE 10-DAY MEANS i3 PRECEC~IPJGVALUE ADJUSTED TO CDKPLETE 20-YEAH PERlnn Table 33.-Windspeed (milh) observed at 3 p.m. P.s.~.;average speed and frequency distribution by direction VII~IISPLEL! - nrtttc~ro~ PFRC~ITAGE FREt30EriCY OF CCCURhE~dCt ilY [IlRFCl IOIU FO9 SF1 ECTFO SPFED 1l~cliEPlEPlTS -CIVtr! TU lFII\ITt~S VEhCEbIT* CFCJV4L tJOINT OMITTED

P~ol).Tti UAY I PiONTIi JUN - - - I - - - L..II,U 3i'ctl). r~t'w I WIND SPEED, MPH 0-3 4-7 I 15-18 19-24 >24 TOTAL AV~, I 0-.x 4-7 8-12 13-18 19-24 >24 TOTAL AVG

IJIR. I!. PCI 'J. PCT Id. t7CT ii. I'CT 1.i. PCT id. !'CT II. FCT SPFEO I k. I'CT N. PCT 11. PCT f'l. PCT 1'1. PCT N. PCT N. PC1 SPEED ------I------?I€ 21 3's 8 13 29 48 5.U I 14 24 13 22 1 2 28 48 3.3 E 14 25 -12 20 26 43 3.2 I 16 27 7 12 1 2 24 41 3.2 SE 26 rj 44 74 4 7 74 124 4.3 I 33 57 53 91 06 148 3.8 S 43 72 69115 4 7 1 P 117 196 4.2 I 49 84 51 87 3 5 103 177 3.7 SW 47 72 Hz i37 5 4 1 ? 151 219 4.2 I 70 120 76 130 6 10 152 261 3.8 55 93 55 97 5 1 ? 116194 3.9 I 49 84 52 89 1 2 102 175 3.7 r+d 27 r5 94 40 2 5 53 8'3 3.7 I 19 33 18 31 3 5 40 69 3.9 h! 21 3-3 11 18 12 33 55 3.5 I 17 29 9 15 2 3 28 48 3.5 CLY 19 32 19 32 .0 I 20 34 20 34 ,O ------I------TOT 269 450 5n5 510 20 33 4 7 ii '3 8 3.8 I 207 492 279 479 17 29 583 3.6

Vi flTP JUL I MONTH AUG --- I - - - IV 1110 sPEErlt ~vti I wIrJD SPEED, MPI-I 0-3 4-7 8-12 15-18 l9-?+ 2 TClTAL AVG I 0-3 4-7 8-12 13-18 19-24 >24 TOTAL AVG

I)IR. 11. PCT J. ?CT I\. I'CT fi. PCT 11. PCT 11. PC1 N. PCT SPEED I N. PCT IN. PCT h. PCT N. PCT N. PCT N. PCT id. PC1 SPEED

l'lr2nlTtt JUFi I MONTtI JUL - - - I - - - C It:': SPFEIJ t I'IPH 1 WIIdD SPEED, WPIi 0-1 4-7 2 13-19 19-24 >2u TOTAL AVG I 0-3 4-7 8-12 13-18 19-24 >2q TOTAL AVG

ilIH. II. PCT PI. PCT iii. PCT 11. PCT #PI.PCT tI. PCT I\. PCT SPFLLl I F. PCT N. PCT N. PCT h. PCT N. PCT N. PCT N. PC1 SPEED ------I------E 1 4 4 14 2 7 7 25 6.5 I 3 5 3 5 2.3 E 7 25 4 14 1 4 12 42 4.31 1 2 3 5 2 3 6 10 5.5 SE 9 32 10 63 10 35 1 4 39 133 5.9 1 14 73 40 65 10 16 3 5 67 110 5.8 S lP b3 28 90 ZD 70 5 13 1 4 72 253 6.6 I 47 77 89 146 47 77 2 3 185 303 5.8 SW 30 105 53 1f>6 27 Y5 1 4 1 9 117 393 5.0 I 44 72 125 205 68 144 15 25 272 445 6.7 e 28 12 42 11 39 31 109 6.1 I 12 20 21 34 11 18 1 2 45 74 5.7 ?JW 414 2 7 h 21 I 3 5 7 11 10 I6 2 3 22 36 7.4 PI 1427414 725 7.41 2 3 4 7 2 3 12 9 15 6.8 CLM I23 2 3 .O ------I------TOT 7th 2h7 125 455 76 767 7 25 2 7 1 4 265 6.0 I 128 709 289 473 170 778 24 39 611 6.2 WINO SPEEO - DIRECTION PERCENTAGE FREQUENCY OF OCCURRENCE BY DIRECTION FOR SELECTED SPEEO INCRENENTS -GIVEN TO TENTHS PERCENT* DECIMAL POINT OMITTED

STATION NUflBER 100202 GISBORNE LO 1951-1960

MONTH JUL I MONTH AUG --- I --- WIND SPEED* VPH I WIND SPEED* MPH 0-3 4-7 8-12 13-18 19-24 >24 TOTAL AVG 1 0-3 4-7 8-12 13-18 19-24 >24 TOTAL AVG DIR.N.PCT NIPCT NePCT bJ.PCT N-PCT NePCT N-PCT SPEED1 NePCT NePCT NePCT N.PCT NaPCT NePCT N-PCT SPEEO ------I------NE 4 14 5 17 1 3 13 il 37 5.9 I 281428 5 20 10.2 E 1313 2 7 414 9.51 14 14 14 3 12 4.7 SE 1 3 6 20 4 14 11 37 6.91 520 312 14 9 36 8.0 S 3 10 29 99 35 119 12 41 2 7 81 276 8.9 I 2 8 15 60 26 104 6 29 1 4 50 200 9.2 SW 7 24 47 160 58 197 25 85 5 17 142 483 9.1 I 10 40 46 184 42 168 18 72 8 32 124 496 9.2 W 620 931 310 2 7 13 21 71 7.01 2 8 24 96 9 36 35 140 6.Y NW 724 724 2 7 13 1758 9.41 416 624 416 14 15 60 6.3 N 13271327 1 3 724 11.91 1 9 728 1 4 9 36 5.4 CLR I ------I------TOT 23 78 106 361 109 371 45 153 10 39 1 3 294 8.8 I 20 80 106 424 87 348 28 112 8 32 1 4 250 8.4

Finklin, Arnold I. Climate of Priest River Experimental Forest, northern Idaho. Gen. Tech. Rep. INT-159. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station; 1983. 53 p.

Detailed climatic description of Priest River Experimental Forest; applies to much of the northern Idaho panhandle. Covers year-round pattern and focuses on the fire season. Topographic and local site differences in climate are examined; also, climatic trends or fluctuations during the past 70 years. Includes numerous tables and graphs. Written particularly for forest managers and researchers.

KEYWORDS: climate, mountain climatology, fire-weather, climatic fluctuations The Intermountain Station, headquartered in Ogden, Utah, is one of eight regional experiment stations charged with providing scientific knowledge to help resource managers meet human needs and protect forest and range ecosystems. The Intermountain Station includes the States of Montana, Idaho, Utah, Nevada, and western Wyoming. About 231 million acres, or 85 percent, of the land area in the Station territory are classified as forest and rangeland. These lands include grasslands, deserts, shrublands, alpine areas, and well-stocked forests. They supply fiber for forest industries; minerals for energy and industrial development; and water for domestic and industrial consumption. They also provide recreation opportunities for millions of visitors each year. Field programs and research work units of the Station are maintained in:

Boise, Idaho Bozeman, Montana (in cooperation with Montana State University) Logan, Utah (in cooperation with Utah State University) Missoula, Montana (in cooperation with the University of Montana) Moscow, Idaho (in cooperation with the University of Idaho) Provo, Utah (in cooperlation with Brigham Young University) Reno, Nevada (in cooperation with the University of Nevada)

✩ U.S. GOVERNMENT PRINTING OFFICE: 1983—776-032/48 REGION NO. 8