THIS SNOWPACK SUMMARY EXPIRED ON February 16, 2021 @ 8:55 am
Snowpack Summary published on February 14, 2021 @ 8:55 am
Issued by Jason Mozol - Bridgeport Avalanche Center

bottom line:

Gale force winds from the SW-W and recent snowfall have created wind slabs and heightened avalanche conditions on N-E-SE aspects, especially near and above treeline. Be on the lookout for smooth pillows, drifts or if the snow suddenly becomes deeper as indicators that you may be on a wind slab. In protected, lower elevation areas, storm slabs may be present on all aspects as new snow begins to bond to old surfaces.

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.

Large wind slabs are likely to be reactive today in near and above treeline terrain. Winds blew at gale force from the SW-W since Friday night, a 111mph gust was recorded above Twin Lakes. Recent snowfall has provided available snow for the wind to deposit on lee aspects, N-E-SE. Winds of this magnitude cause slabs to form in unusual places such as farther down drainages and across ridges than we are used to. Looking ahead, more wind and snow will arrive Sunday night through Monday and build on the current wind slab problem. 

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.

8” of new snow fell in the last day and 20” in the last 72 hours on top of variable crust surfaces. Primarily below treeline, small to large storm slabs may be encountered in isolated areas. More snowfall tonight through Monday will add to the slab. This interface can be slow to bond, signs of instability such as whoompfing, cracking and recent avalanche activity are indicators of a reactive storm slab problem.  

Snowpack Discussion

The active weather pattern we are currently in has brought with it the development of both wind and storm slabs. The last of the snow is expected to fall Monday night. Recent snowpit tests suggest the new snow is slowly bonding to the crusts below, signs of instability and unconsolidated snow are telling that this bond needs more time to strengthen. Winds are going to continue to be strong throughout the week requiring continued assessment of the wind slab problem.  

 

Throughout the season we have been tracking a layer of large facets at the bottom of the snowpack on NW-N-E aspects. Continued testing and observations indicate failure of this layer is unlikely and that the facets have begun the rounding process. It will take some time for these facets to fully heal. In the meantime, if this problem is to be encountered it would be in shallow spots of the snowpack, such as convex rolls or near trees and rocks, where the weak layer is closer to the surface and result in large avalanches.  

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 14 deg. F.
Max. temperature in the last 24 hours: 24 deg. F.
Average wind direction during the last 24 hours: SW-W
Average wind speed during the last 24 hours: 30+ mph
Maximum wind gust in the last 24 hours: 111 mph
New snowfall in the last 24 hours: 8 inches
Total snow depth: 99 inches
weather

A break in the weather today with clear skies and temperatures around freezing in the mountains. One last storm of our current active pattern arrives tonight and lasts through tomorrow. This storm is expected to be warm and bring 3-6 inches of snow to the mountains with rain at lower elevations. Clear skies, cooler temperatures and wind is on tap for the upcoming week.  

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Sunday Sunday Night Monday
Weather: Partly cloudy becoming sunny Most cloudy. Slight chance of snow Mostly cloudy, chance of snow
Temperatures: 29-35 deg. F. 22-27 deg. F. 32-40 deg. F.
Wind direction: NW W W
Wind speed: 15mph, gusting to 40mph 15-20mph, gusting to 45mph 15-25mph, gusting to 70mph
Expected snowfall: 0 in. Up to 1 in. Up to 3 in.
For above 10000 ft.
  Sunday Sunday Night Monday
Weather: Sunny then becoming partly cloudy Mostly cloudy, chance of snow Mostly cloudy, snow likely
Temperatures: 22-28 deg. F. 17-22 deg. F. 24-32 deg. F.
Wind direction: NW W W
Wind speed: 15-30mph, gusting to 45mph 20-35mph, gusting to 70mph 35-55mph, gusting to 85mph
Expected snowfall: 0 in. Up to 2 in. Up to 3 in.
Disclaimer

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.