THIS SNOWPACK SUMMARY EXPIRED ON December 30, 2016 @ 3:37 am
Snowpack Summary published on December 28, 2016 @ 3:37 pm
Issued by Kyle Van Peursem - Bridgeport Avalanche Center
Avalanche Character 1: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

With daytime temperatures expected to rise above well above the freezing mark Wednesday and Thursday, expect wet loose avalanche activity on southerly slopes in the afternoon. Though these aren't expected to be large, they could be big enough to knock you off your sled and could be dangerous in high consequence terrain.

Avalanche Character 2: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Exposed northerly slopes were loaded during the previous storm and some of these slabs may have released during or just after the storm. Though the potential of triggering a wind slab will continue to diminish as time goes on, it is still recommended to avoid any wind loaded slope steeper than 35 degrees for now as these slopes are still capable of producing an avalanche large enough to bury/injure a person.

Snowpack Discussion

Special Announcement: Hello everyone, the BWRA is now open and the 2016/17 season has officially begun. Please remember to fill out a free permit at one of the self-service kiosk stations located at either the People's Gate or at Sonora Pass. This is required prior to accessing the BWRA. For this season, we will have a dedicated Avalanche Forecaster as well as a Winter Snowmobile Ranger and other volunteers helping to bring you the most up-to-date information on the conditions and avalanche danger in the BWRA. More information about this season's staff can be found at the bottom of this page under 'People'. A Snowpack Summary will be published several times a week, or more depending on conditions and the avalanche danger. This will also be posted at the self-service kiosk stations during the weekend.

Snowpack History: The snowpack is off to a decent start this year, especially above 9000', where above average precipitation has fallen mostly as snow. Since October, precipitation at the Leavitt Lake SNOTEL station (9617') is 159% of average and the total snow water equivalent (SWE, or the amount of water weight in the snowpack) is 103% of average. Meanwhile, almost a 1000' lower at the Sonora Pass SNOTEL station (8770') total SWE is 89% of average while precipitation is 149% of average. As we can see, the early season storms have been warm with higher freezing levels favoring locations above 9000'. We have seen two large storms come through in December which has helped to setup the bulk of our snowpack so far this season. The first storm came through between December 15th and 16th and deposited nearly 30" of snow at the Leavitt Lake SNOTEL station and 14" at the Sonora Pass SNOTEL station. This storm came in warm and started as rain for elevations below 10,000', forming a crust between the old/new snow interface, which is now buried mid-pack. The second storm came through between the 23rd and 24th bringing 12-16" above 8500' in the BWRA.


Current Conditions: Overall, the snowpack is setup well with 1-1.5' of somewhat consolidated new snow on top of stronger, snow from the Dec 15-16 storm. Though there is a mid-pack crust below the Dec 15-16 snow, it does not appear that this layer has been, or is, reactive with no observations of large slab avalanches in the BWRA. Strong southerly winds associated with the last storm have created wind slabs on upper northerly aspects but have been only minimally reactive.

recent observations

Riding conditions have been pretty decent since the last storm with cold temps keeping the snow surface soft. Riders have been making some aggressive lines already, even in steep avalanche terrain. A few dry loose avalanches were seen in steeper terrain but nothing else was observed. We did see a few crown lines from old avalanches on the ridgelines above the PCT crossing at Sonora Pass, but it is unknown if these failed from the most recent storm. Of note: We observed some near surface weak layers beginning to form on shady NW-NE slopes yesterday (Tuesday) including small surface hoar crystals and a thin radiation-recrystallization crust just below the surface. Though not dangerous now, once buried these layers can act as a persistent weak layer in the snowpack. It will be important to monitor the presence of these layers prior to the next storm.


Since the Dec 23-24 storm, clear and cold conditions have prevailed, with morning temps dropping to near 0F in the BWRA. As a large ridge of high pressure builds in to our area for the next couple of days, temperatures will rise well above the freezing mark, even above 9000'. The next system moves in on Friday bringing cooler temperatures, increased clouds, and a chance for some minor snow accumulations through the weekend.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Sunny Clear Sunny
Temperatures: 40-45 deg. F. 17-22 deg. F. 40-45 deg. F.
Wind direction: WSW WSW WSW
Wind speed: 5-10 mph 5-10 mph 5-10 mph
Expected snowfall: 0 in. 0 in. 0 in.
For above 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Sunny Clear Sunny
Temperatures: 33-41 deg. F. 15-23 deg. F. 34-42 deg. F.
Wind direction: WSW WSW SW
Wind speed: 5-10 mph 5-10 mph 5-10 mph
Expected snowfall: 0 in. 0 in. 0 in.

This snowpack summary applies only to backcountry areas in the Bridgeport Winter Recreation Area. Click here for a map of the area. This snowpack summary describes general avalanche conditions and local variations always occur. This snowpack summary expires in 48 hours unless otherwise noted. The information in this snowpack summary is provided by the USDA Forest Service who is solely responsible for its content.