THIS SNOWPACK SUMMARY EXPIRED ON February 5, 2017 @ 9:13 pm
Snowpack Summary published on February 2, 2017 @ 9:13 am
Issued by Kyle Van Peursem - Bridgeport Avalanche Center

bottom line:

Thursday:Isolated human triggered avalanches will be possible on steep wind loaded slopes in the BWRA due to 6" of new snow and strong SW winds

Friday: Avalanche danger will rapidly increase through the day as a storm system brings heavy snow and strong winds to the Sonora Pass area. Natural avalanches will be possible and human triggered avalanches will be likely, especially on wind loaded slopes steeper than 35 degrees.

Saturday and Sunday: Avalanche danger will subside as the new snow and wind slabs begin to strengthen during a break between storms. Human triggered avalanches will still be possible on 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.

Strong winds will accompany this current storm system with winds sustained at 30-45 mph gusting to near 100 mph on exposed ridgelines. This will rapidly load NW-N-NE-SE facing slopes, especially on Friday, when the strongest winds and heaviest snowfall is expected. Triggering a wind slab will be likely on Friday, especially with a sled. Over the weekend we will get a break in between storms allowing wind slabs to strengthen and bond to the underlying snowpack. Though triggering these features will become more difficult over the weekend, it will still be possible and it is recommended to avoid any wind loaded slope steeper than 35 degrees during this time.

To identify wind slabs, use clues such as blowing snow, new cornice formations, and newly formed wind pillows to identify and avoid slopes with likely wind slab development.

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.

6" of new snow was measured this morning up at Sonora Pass. Another 7-13" is expected tonight through the end of the day on Friday bringing the total new snow from this storm up to about 20". Though this isn't a huge load added to the snowpack, at least compared to what got last month, the new snow will fall on a variety of surfaces including hard wind boards, melt-freeze crusts, and even some near-surface facets or surface hoar in shady sheltered areas near tree line. This means the new snow will not bond very well and will initially be very reactive to stress. Human triggered storm slab avalanches will be likely on Friday, and possible over the weekend on slopes steeper than 30 degrees. Look for signs of instability including cracking, collapsing, and whoomphing and avoid travel on these slopes.


After a 10 break in weather, the storm pattern opens up again with a series of storms expected Thursday/Friday, Monday, and Wednesday of next week. The first wave of precip came through last night bringing a modest 6" of snow. We will have a break in weather today with the second, stronger wave moving through tonight through Friday, bringing an additional foot of snow. Total snow accumulations could top out at around a foot and a half by Saturday morning. Temperatures will remain in the upper 20's through the day on Friday meaning the snow will be on the heavier side. We will get a break between storms over the weekend and conditions are expected to be nice with mostly cloudy skies on Saturday and more abundant sunshine on Sunday accompanied by lighter winds.


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.