THIS SNOWPACK SUMMARY EXPIRED ON February 13, 2017 @ 10:00 am
Snowpack Summary published on February 10, 2017 @ 10:00 am
Issued by Kyle Van Peursem - Bridgeport Avalanche Center

bottom line:

Friday, Feb 10th:  Heavy new snow and strong SW winds will lead to increased avalanche danger through the day.  Human triggered avalanches will be likely and natural avalanches will be possible, especially on wind loaded slopes steeper than 35 degrees.

Saturday-Sunday, Feb 11th-12th:  The avalanche danger will decrease over the weekend as the new snow and wind slabs gain strength and bond to the underlying snowpack.  Natural avalanches will be unlikely but human triggered avalanches will still be possible in certain locations, including wind loaded slopes steeper than 35 degrees.   

Avalanche Character 1: 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.

On Friday, strong SW winds combined with over 2' of new snow have loaded, and will continue to load, exposed leeward slopes, which include NW-N-NE-SE facing slopes.  Any natural avalanche activity likely released overnight and this morning but it will still be likely for a snowmobiler to trigger a wind slab on slopes steeper than 35 degrees through the day on Friday.  This danger will subside over the weekend as the winds slabs gain strength but the added weight of a snowmobile may be enough to trigger an avalanche on Saturday and Sunday.

Looks for signs of recent wind loading such as cornices, blowing snow, wind drifts, wind pillows, ripples on the snow surface, and other wind created textures to help identify where wind slabs may exist and use this information to avoid these problematic wind slabs.

Avalanche Character 2: Storm Slab
Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize.

Since last night, SNOTEL stations in the BWRA recorded about 2' of new snow. Luckily, temperatures dropped through the night from the mid 30's to the upper 20's leading to right side up new snow (lighter snow on top of denser snow). The new snow fell on a mostly wet snow surface and likely bonded well to the old snow, though some crusts may be present in higher elevations. Generally, storm slab issues should not be much of a problem but could still be triggered by a rider on slopes steeper than 35 degrees.

Snowpack Discussion

Over the past 5 days, snow levels were primarily between 9000-9300', though temporarily rose to above 9600' on Wednesday night/Thursday morning. Below that, so much rain fell on the snowpack that well-established channels formed for water to drain out the bottom of the snowpack, greatly decreasing the likelihood of deep wet slab avalanches. The biggest instability issue is now new snow and wind slabs, which will decrease over the weekend.

recent observations

The most recent field observation was from Wednesday where rain was observed up to about 9300' and wet heavy snow was observed above that. Numerous wet loose avalanches were seen in Voodoo Bowl but no signs of wet slab avalanches were observed. Numerous mid storm instabilities were seen in a snow pit at 9800' but none showed any propagation potential in my stability tests.


The latest AR event came through Thursday night bringing colder air and about 2' of new snow as of 10 am Friday. Another 6" of snow is expected through the rest of the day before high pressure builds in for the weekend, lasting through Thursday next week.

Since Sunday night, a series of ARs brought another round of impressive precipitation totals to the BWRA. Here are the totals as of 10 am Friday:

Sonora Pass SNOTEL (8770'): 45" snow / ~5" rain / ~10" total precip
Leavitt Lake SNOTEL (9617'): 65" snow / ~0.8" rain / ~14" total precip. Total snow depth now at ~19'!!

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Friday Friday Night Saturday
Weather: Cloudy. Snow Mostly cloudy. Snow showers in the evening, then chance of snow after midnight Mostly cloudy.
Temperatures: 34 to 42 deg. F. 18-24 deg. F. 22-27 deg. F.
Wind direction: Southwest West North
Wind speed: 15 to 25 mph with gusts to 50 mph 10 to 15 mph. Gusts up to 45 mph decreasing to 35 mph after midnight Light winds then 15 to 20 mph with gusts to 45 mph in the afternoon
Expected snowfall: 2 to 11 in. 1-4 in. 0 in.
For above 10000 ft.
  Friday Friday Night Saturday
Weather: Cloudy. Snow Mostly cloudy. Snow showers in the evening, then chance of snow after midnight Mostly cloudy.
Temperatures: 28-36 deg. F. 12-18 deg. F. 15-20 deg. F.
Wind direction: Southwest West North
Wind speed: 25 to 40 mph with gusts to 75 mph 20 to 35 mph. Gusts up to 60 mph decreasing to 50 mph after midnight 10 to 15 mph with gusts to 35 mph increasing to 20 to 30 mph with gusts to 65 mph in the afternoon
Expected snowfall: 5-10 in. 1-4 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.