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 manage- ment, 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 accumula- tion 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 informa- tion 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 in- cluded. 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,