2019-2020 Annual Report Bridgeport Winter Recreation Area

2019-2020 Annual Report

Bridgeport Winter Recreation Area

Report to Jan Cutts, District Ranger Bridgeport Ranger District, Humboldt-Toiyabe National Forest

INTRODUCTION

The purpose of the 2020 Annual Report is to establish a baseline document to guide future end of winter season reports. New for winter 2020 is implementation of the National Avalanche Center’s recommendation that resources are best directed towards OSV ranger training and education which will develop stability in the winter snowmobile ranger program. The snowmobile patrol program is now focused on maintaining consistent presence in the Bridgeport Winter Recreation Area. Staff training, review of current practices and policy pertaining to field operations and avalanche awareness will assist in the overall appearance and content of the website and public service information.

BACKGROUND

The Bridgeport Winter Recreation Area (BWRA) was designated by Congress by the Omnibus Public Land Management Act of 2009. It is the first winter recreation area to be congressionally recognized and designated. The BWRA is a small area of approximately 7,254 acres, encompassing two alpine and subalpine watersheds that provide excellent skiing and sledding terrain and shown in Figure 1.

The boundaries of the BWRA follows the watersheds of McKay and Leavitt Creek. MacKay and Sardine Creek watersheds encompass approximately 3,800 acres and define the north and northwest boundaries of the BWRA. The western boundary of the Leavitt Creek watershed is the Sierra Crest. Total acreage of the BWRA is 7,254 acres, similar in size to the Mammoth Lakes Basin.

People’s Gate

Sonora Pass Bridge SnoTel

Leavitt Meadows SnoTel

Leavitt Lake SnoTel

Figure 2. McKay Creek and Leavitt Creek watersheds and Sno-Tel stations in the BWRA. Three NRCS (Natural Resources Conservation Service) Sno-Tel stations are located in the BWRA (Figure 2), located along an elevation gradient beginning at 9,600 ft near Leavitt Lake to 7,200 ft at Leavitt Meadows. Leavitt Lake Sno-Tel station is located a few hundred yards north and east of Leavitt Lake (Figure 2). The Sonora Pass Bridge station is located at 8,700 ft in the McKay Creek drainage. Leavitt Meadows is located at 7,200 ft. Climate records extend from the 1980’s to the present, offering an unusual opportunity to analyze long term trends in air temperature, and variability in snowpack accumulation patterns and precipitation.

The Pacific Crest Trail (PCT) traverses across 2 miles of the BWRA near Sonora Pass. The PCT was designated by the National Trails System Act of 1968 as a non-motorized/non-mechanized trail to provide recreation opportunities for winter and summer recreation. The Omnibus Public Land Management Act directed the Forest Service to establish an appropriate crossing of the PCT for winter motorized users from the BWRA to the adjacent Stanislaus National Forest. Snowmobiles traveling west up the McKay Creek drainage can proceed north to the Sonora Pass Road via the PCT Crossing Area. Most of the terrain within the McKay Creek drainage and the PCT Crossing Area is avalanche terrain.

The PCT Crossing traverses below Unnamed Peak (10,900 feet) and above the prominent rock formation in the left center of Figures 3 and 4. The PCT Crossing traverses across shaded, north facing slopes where weak faceted snow and depth hoar are common. Prevailing southwest to west winds transport snow from the west side of the ridge, creating wind deposits on the east facing slopes seen in the photograph. North and east facing slopes above treeline receive little solar radiation during the winter and snowpacks are generally much colder than on southeast to west facing slopes. Weak snow often persists during the entire winter.

These slopes also receive significant wind loading from winter storms and avalanches often release naturally during and immediately after winter storms. It is common to find weak faceted snow in shallow snowpacks and can surprise winter recreationists who are used to a forgiving snowpack that allows careless route finding and descents with no consequences. Figure 4 shows the PCT Crossing in low snow conditions on January 31, 2020.

The BWRA is open to snowmobiling from December or January until April 15 each year. Permits are required to ride in the BWRA and are easily obtained at the People’s Gate trailhead. In 2017, 1,200 permits were issued, though hand written permits are not obtained by all users, leading to under reporting errors. Online permits will be available for winter 2021: online permitting will make it easier for users to obtain permits and should provide more realistic use figures.

Winter use numbers are generally controlled by snow conditions. Heavy snowfall winters such as 2017 and 2019, attract higher numbers of users than drier winters when visitation seems to be better correlation by new snowfall than weekend use. 3

Figure 3. PCT Crossing, January 31, 2020. Photo credit Brent Dull. Snow depth at Leavitt Lk was 41 inches.

The avalanche terrain in the PCT Crossing area is easily seen in an average year. Apr 1, 2013.

Figure 4. PCT Crossing Area, Apr 1, 2013. Snow depth at Leavitt Lk was 104 inches. Photo credit, Sue Burak 4

SNOW, WEATHER AND AVALANCHES, WINTER 2019-2020

The winter of 2019-2020 had a promising start in late November when an impressive low- pressure system brought low snowlines and significant snow to the Eastern Sierra. With an unusually cold airmass for late November, the 5-day period of wet and cold conditions dropped 44 inches of snow and 8 inches of water equivalent at the Leavitt Lake sensor at 9,600 ft. The Sonora Pass Bridge station picked up 31inches of new snow and 4 inches of water equivalent. Leavitt Meadows picked up 14 inches of new snow and 1.3 inches of water equivalent. This storm was the biggest storm of the season and one of the top ten storms since 2000.

Figure 5. Initial phase of deepeing meteorological “bomb” storm. November 26, 2019.

The higher elevations of the BWRA picked up 23” of snow in December, about half of the long- term December snowfall average. In January, the prevailing atmospheric pattern shifted toward one that favored occasional weak-to-moderate storms, but no large precipitation events. Leavitt Lake picked up 24” of snow while Leavitt Meadows only received 9” of measurable snowfall. After January 18, only 8 inches of snow fell at Leavitt Lake until March 3.

In February, many places throughout the State saw zero precipitation for the first time in over 100 years- a remarkable record for what is typically the wettest months of the year. The dry warm weather was accompanied by continuous east and northwest winds that stripped snow from ridgetops and created icy crusts and thick wind slabs developed throughout the BWRA. Weak faceted snow that formed in December and January remained in the snowpack through April.

Figure 6. Persistent northwest winds over the Sierra Crest, February 2020.

The average daily temperature in February 2020 was 29.6 F at Leavitt Lk and 33F at Leavitt Meadows. Snow depths taken from snow pits ranged from 30 to 36 inches- shallow compared to the 20-year average February snow depth of 99.4” at Leavitt Lake. Shallow snowpacks develop weak faceted grains in response to higher gradients of temperature from the base of the snow to the surface and can be triggered by skiers, riders and heavy storm snow loading throughout the winter.

The season-to-date precipitation deficits gradually increased during February with significant snowmelt occurring on Highway 108 from People’s Gate to the 8,000 ft elevation. Patchy snow and long stretches of asphalt made snowmobile access difficult in February and early March. A side by side was used to drive up to the 8000 ft elevation where sleds were stored. The USFS side-by-side used to transport rangers and gear to snowline is shown in Figure 7.

Figure 7. Loading the side by side for a trip into the BWRA. Photo credit, Sue Burak

Figure 8 displays snowfall accumulation at Leavitt Lake, Sonora Pass Bridge and Leavitt Meadows from November through mid-April.

2020 Season snowfall, SnoTel stations in the BWRA Leavitt Lake, Sonora Pass Bridge, Leavitt Meadows 120

100

40 Snowfall, inches Snowfall,

0 11/26/2019 12/26/2019 01/26/2020 02/26/2020 03/26/2020

Leavitt Lk Snow Depth, in Sonora Pass Bridge Leavitt Meadows snow depth

Figure 8. Snowfall accumulation, winter 2019-2020. Winter snows returned to the BWRA in mid-March with peak accumulation occurring during the second week of April. The plot shows that elevation is a strong predictor of snowfall accumulation (R2= 0.83) in the BWRA. During the prolonged dry spell from mid-January through early March, Leavitt Meadows melted out by March 1 and access to the BWRA required driving on Highway 108 for several miles until snowline was reached at about 8,200 ft.

WINTER RETURNS

Winter returned to the Eastern Sierra in mid-March, coincident with the COVID-19 pandemic. 30 inches of new snow fell from March 14-15, bringing many riders to the BWRA. Patrollers reported three rider-triggered avalanches and a naturally occurring avalanche in Leavitt Bowl. One avalanche (not shown) was remotely triggered by a rider on flat ground in the Sardine Creek drainage. Remote triggering is unusual in the Eastern Sierra because snowpacks are much deeper than the snowpack of 2020; however, the shallow snowpack promoted persistent weak layers responsible for remote triggering.

Figures 9 and 10. Human-triggered avalanches, March 17, 2020. Photo credits, Brent Dull.

Figure 10. Human-triggered avalanche, Leavitt Lake area, March 17, 2020.

Cold winter storms returned from April 4 -10. An unusually cold and strong spring atmospheric river brought 30” to the Leavitt Lake area, almost two feet to Sonora Pass Bridge at 8,700 ft, and 18” to Leavitt Meadows. Snowmobile patrols ended in late March and the program lost essential observations of snowpack and spring avalanche activity. The importance of snowpack and avalanche observations during unusual weather events is key for patrollers’ understanding of conditions preceding avalanche activity. It is likely that many large human-triggered and natural

8 wet slab avalanches occurred in the BWRA because observations of large wet slab avalanches were reported from Virginia Lakes all the way south to the Whitney region.

April 1 has been traditionally the time of year when snowpack accumulations peak. On April 1, 2020, the water content in the snowpack at Leavitt Lake, elevation 9,600 ft., was 33% of the long-term average. Due to late season storms from April 4-10, peak accumulations at Leavitt Lake and Sonora Pass Bridge (8,750 feet) occurred during the second and third week of April. The late season atmospheric river brought multiple feet of snow to the BWRA, bringing the snowpack at Leavitt Lake up to 77 percent of the long-term mean.

Date of Peak Date of percent of SWE Location peak snow Accumulation, peak 1981-2010 inches depth Inches SWE mean Leavitt Lake 10-Apr 122 13-Apr 40 77 Sonora Pass 10-Apr 63 14-Apr 17.1 66 Bridge Leavitt Meadows 27-Dec 22 03-Feb 6.5 81 Table 1. Date of peak snowpack accumulations in the BWRA.

Table 1 shows the time lag between the date of peak snowpack depth and the date of peak water content in the snowpack. For example, Leavitt Lake snow depth peaked at 122 inches on April 10, 2020 but the peak water content in the snowpack at Leavitt Lakes peaked 3 days later on April 13. The lag is due to the fact that snow pillows adjust to the mass of new snow over the course of 24 to 48 hours. Post-storm wind transport will also contribute to the lag times.

Leavitt Meadows snowpack depth can be used as an index to estimate whether there is sufficient snow to ride snowmobiles from the People’s Gate. Field operations were hampered in January, February and March by patchy snow and long stretches of asphalt. Snowmobile access was difficult so a side by side was used to drive up to the 8,000 ft elevation where sleds were stored. Above 8,000 ft, bare asphalt areas were widely scattered, but ice flows by the Leavitt Lake turnoff required careful navigation.

AVALANCHE TERRAIN

Avalanche terrain in the BWRA generally falls into three classes using the Avalanche Terrain Exposure Scale developed by Parcs Canada in 2004 by Grant Statham and Bruce McMahon.

Simple terrain is low angle and primarily forested terrain. For example, the groomed trail to Leavitt Bowl has some forest openings that could expose travelers to the runout zones of large,

9 infrequent avalanches. Challenging terrain in the BWRA includes bowls areas with convex entrances, terrain that exposes riders to well defined and active avalanche paths, and terrain traps. Exposure to well defined active avalanche paths can be managed with careful route finding.

The third category of the ATES system, Complex Terrain, includes areas in the BWRA such as Sardine Creek, terrain leading to Leavitt Peak and the PCT Crossing Area. There is exposure to multiple overlapping avalanche paths and large expanses of steep, open terrain, with terrain traps below that offer minimal options to reduce exposure.

Classifying popular and less visited areas of the BWRA will help identify levels of use, rider skill categories and help target avalanche education messaging and education approaches.

Figure 9. Complex terrain in Sardine Creek, March 2020. Photo credit, Brent Dull. Travel in the bottom of the Sardine Creek drainage exposes riders to multiple runout zones from northwest to southeast slopes.

The Avalanche Path Attributes shown in Table 2 should be expanded to include Sardine and Mc- Kay Creeks, Leavitt Lake and Leavitt Bowl and the short and dangerous paths below Leavitt Peak.

The physical attributes of the avalanche paths in the PCT Crossing Area are displayed in Table 2.

AVALANCHE PATH ATTRIBUTES

Elevation Starting Estimated Starting difference Starting zone Average maximum zone starting zone Location zone slope avalanche runout elevation to estimated aspect angles, track angle slope range, ft maximum degrees distance runout, ft Unnamed 10,750 ft 1400-1600 Peak to 10,970 750-900’ ft. NE 38-45 36 avalanche ft vertical drop paths Unnamed 1300-1500 10,600 to 700-800’ peak ridge NNE 35-45 36 ft. 10,750 ft vertical drop paths Short avalanche 9850- 100-150 E, ENE 35-40 35-40 300-400 ft paths above 9750 ft. vertical feet terrain trap Paths on north side of pass between 10,200 to NNE to 400-700’ 1400-1500 35-40 30-35 Mc Kay 10,400 ft NE vertical drop ft Creek and Sardine Creek

Pass between Mc Kay Creek and 200-400’ 10,400 ft NW 35-40 30-35 700-800 ft Sardine vertical drop Creek, NW aspect Lower route 75-250’ Various N, NE 35-40 35-40 350-450 ft paths vertical drop

Table 2. PCT Crossing Avalanche Path Attributes

Figure 11. Illegal trespass in the PCT Crossing area in the spring.

CLIMATE

The Sonora Pass area receives more snow accumulation than the Mammoth Mountain area 50- 60 miles to the south. During an average winter, the Leavitt Lake snow course (9,600 ft) contains 50.8” of water in about 110-120 inches of snow on April 1. This represents an average of 30 years of measurements conducted by Pacific Gas and Electric snow surveyors. For comparison, the Mammoth Pass snow course (9,300 ft) has an average April 1 snow water content of 42.5” in about 100 inches of snow depth. Both Mammoth Pass and Leavitt Lake receive heavy amounts of snow compared to surrounding mountain areas due to orographic lifting and channeling of moist Pacific air masses up the San Joaquin and Stanislaus River canyons.

The snow avalanche climate of the Sonora Pass area is characterized by mild winter temperatures, large amounts of precipitation and more frequent avalanches than intermountain and continental climates. Average daily winter temperatures (December through March) from 1989 to 2020 at Leavitt Lake are 270 F and 300 F at Leavitt Meadows. Most avalanche activity occurs during or after storms when high rates of snowfall and strong west and southwest winds create dangerous wind slabs on north to east facing slopes.

WARMING WINTERS

The National Weather Service and the National Resources and Conservation Agency (NRCS) use 30-year averages to define “climate normals”. These are used to report “normal” high and low temperatures. They are updated every ten years. The current “normal” temperatures or “percentage of normal” temperatures are based on the 1981-2010 average. The 1981-2010 average period was a period of increasing temperatures. The 1980’s to 1990’s were relatively cold with increased warming from 2000 to 2010. The new climate normal will be issued soon and will be based on the 1991-2020 averages. In ten years, 2030, these new “normals’ will likely become obsolete. Winter average temps are much warmer than winters that occurred in the 20th century.

Table 3 displays the difference in average winter temperatures at the SnoTel stations in the BWRA between average winter temperatures in the 20th century and the most recent 20 years.

Average Daily Air Temperature in degrees, Fahrenheit Dec-March Station Elevation 1989-2000 2001-2020 Leavitt Lake 9,600 ft 25 28 Sonora Pass Bridge 8,700 ft 25.8 29 Leavitt Meadows 7,200 ft 28.2 31

Table 3. The data show there has been 3 degrees F of warming at all elevations in the BWRA since 2000. While further statistical tests are needed to better define the change in temperature, the trend is clear. The historic temperature records of Leavitt Meadows from 1989 to 2020 show a clear upward trend (Figure 12).

Average Daily Winter Temperatures, 0F November through April, Leavitt Meadows 1989-2020 65 55 45 35 25 15

Air Temerature, F Temerature, Air 5

-5

03/31/1996 01/12/1999 04/24/2001 02/26/2015 12/09/2017 04/05/1990 03/09/1991 02/10/1992 01/14/1993 12/19/1993 11/23/1994 04/27/1995 03/05/1997 02/07/1998 12/17/1999 11/20/2000 03/29/2002 03/03/2003 02/05/2004 01/09/2005 12/14/2005 11/18/2006 04/22/2007 03/26/2008 02/28/2009 02/02/2010 01/07/2011 12/12/2011 11/15/2012 04/19/2013 03/24/2014 01/31/2016 01/04/2017 11/13/2018 04/17/2019 11/01/1989 13

Figure 12. Trend in average air temperature, 1989-2020, Leavitt Meadows.

The Leavitt Meadows Sno-Tel station historic records of snow depth, snow water equivalence and temperature extend from 1982 to the present. Most years (32 out of 39, 82% of the time), there is not enough snow on the ground during the month of November at Leavitt Meadows to ride a snowmobile, assuming 6-12” of snow on the ground is adequate for snowmobile access. The years when snowmobile access was possible in November was 2003, 2004, 2009, 2010 and 2019.

Historically, there is more snow on the ground during the month of December but the likelihood of having adequate snow on the road to ride from People’s Gate to Leavitt Meadows is about 50- 60%. The east to southeast facing switchbacks above Leavitt Meadows generally have patchy snow cover. People’s Gate is similar in elevation to Leavitt Meadows so it is reasonable to expect that so most of the time in early winter, access to Highway 108 and the Leavitt Lake Road requires riding on asphalt or using alternative transportation to access snowline.

OPERATIONS WINTER 2020

Lack of snow in January, February and early March required long approaches to snowline via the side by side and sleds. Consistent weekly access was difficult and there were weeks when 2 to 3 trips per week were not possible.

Maintaining consistent visits to BWRA in order to do enough field work to produce 2 to 3 snowpack summaries per week was constrained by long stretches of pavement from People’s Gate to the 8,000 ft elevation. Another constraint on access is storm snow- snowfalls of 12 to 18” or more can limit snowmobile access by the patrol rangers unless the MWTC grooms the road or public snowmobile traffic compacts storm snow to manageable conditions.

A minimum of 2-3 trips per week to observe snow conditions, recreation use patterns, collect avalanche observations and dig snow pits are necessary to post 2 to 3 snowpack summaries a week. When significant storms are forecasted, knowledge of preexisting snow conditions and snow pit profiles is essential to forecasting snow and avalanche conditions during and immediately after storms. Scheduling field days prior to storms will assist avalanche forecasting.

Avalanche forecasting is also hampered by the lack of wind speed and direction data from the area. While snow and precipitation accumulation rates are available from the SnoTel sensors, the only data resource that estimates wind speed and direction is Windy.com and HRRR 1 km resolution wind products. This season, National Weather Service forecasts along with wind information from windy.com provided general wind information at 3 km grid scale. The

14 windy.com website was useful to visualize surface, 700 and 500 mb winds, air temperature and precipitation.

The program needs a portable weather station (https://datagarrison.com/). The Data garrison portable weather station has a long history of use in Inyo and Mono Counties and avalanche centers throughout the West.

A webcam sited at Leavitt Lake would also be very helpful to document post storm avalanche activity when access to Leavitt Lake is not possible due to the amount of new snow. Often post storm winds will redistribute snow and erase signs of post storm avalanches.

ACCOMPLISHMENTS

• The BWRA/Bridgeport Avalanche Center website provides the public with important weather, snow and avalanche conditions. Andy Anderson of the Sierra Avalanche Center gave access to the meteorological tech and patrol rangers. Snowpack summaries, snow pit profiles and general conditions reports were posted in January, February and early March.

• Despite adverse snow conditions, the patrol rangers made 40 trips to the BWRA and learned to ride in steep, complex mountain terrain.

• Avalanche training and forecasting exercises continued online after the COVID-19 closures of the BWRA. Patrollers wrote practice avalanche forecasts and snowpack summaries, using avalanche problems and the US Avalanche Danger Scale.

• The BWRA is unique in the United States because the US Marine Corps operates a Mountain Warfare Training Center at Pickel Meadows just outside the BWRA boundary at People’s Gate. Up until the winter 2020, there was no coordinated avalanche response plan to address the different jurisdictions that would be summoned in case of an avalanche incident involving partial to total burial and fatalities required response from the USFS and/or the Marine Corps. A draft avalanche response plan was written in April and May with input from the Marine Corps. The COVID-19 pandemic ended the collaborative effort, but the response plan will be reviews and completed during the winter of 2021.

Recommendations

1. Upgrade the OSV program by hiring seasonal patrollers at the GS-6 pay scale. 2. Continue vehicular access to snowline by staging sleds at 8,000 ft. 3. Ongoing avalanche awareness and avalanche forecasting training for patrol staff. 4. Update the website once or twice a week. 5. Utilize social media to encourage users to report observations 6. Snowmobile avalanche courses need to be taken every season to keep current with policies and best practices. 7. Provide avalanche awareness training to the public 8. Purchase and in install a DataGarrison Weather Station 9. Webcam at Leavitt Lake 10. Expand coverage to the Sawtooths and Virginia Creek areas.

Figure 13. Digging out the Sonora Pass sign, March 2010.