THIS SNOWPACK SUMMARY EXPIRED ON February 20, 2021 @ 8:20 am
Snowpack Summary published on February 18, 2021 @ 8:20 am
Issued by Jason Mozol - Bridgeport Avalanche Center

bottom line:

It remains possible for you to trigger a wind slab avalanche on middle to upper elevation slopes facing North through East through Southeast. Several storms and strong winds over the last week have built and redistributed these dense slabs of snow. Avoid steep wind loaded slopes that appear smooth or pillowy or have dense, hollow sounding snow. Be on the lookout for signs of instability like cracking and collapsing. Also be prepared for variable snow conditions in the backcountry with a variety of hard and breakable crusts from recent sun, wind, and warm temperatures.

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.

Over the last week we experienced a significant period of strong winds, generally out of westerly directions. These winds were coupled with some small to medium sized storms. The winds built and redistributed the snowfall into wind slabs on middle and upper elevation slopes. At these elevations you are most likely to find a wind slab on N-E-SE aspects. Yesterday’s brief shift to NE winds may have formed some small new wind slabs on SW-W aspects at upper elevations, but these will be quick to erode today with last night’s shift back to westerly winds. 

The wind slabs may be stubborn to trigger and not show signs of instability, but it is still possible for you to trigger one. Avoiding steep wind loaded slopes will be the best way to stay out of harm's way. These slopes will appear smooth and pillowy, and unfortunately, will also be the most attractive steep terrain to ride. Give these wind slabs more time to fully heal; instead look for slopes protected from the wind or that have been wind scoured. 

With a small storm passing by to our north, westerly winds will increase today into tomorrow. There is minimal snow available for transport and very little snow forecasted, so significant new wind slabs are unlikely to form. However, if the storm overproduces, be on the lookout for fresh wind slabs.

Snowpack Discussion

Unfortunately last weekend’s deep powder has mostly been blown away and snow conditions are currently very variable in the backcountry. The last week of strong winds created both wind slabs and a mixed bag of wind affected snow textures from wind crusts and wind board, to large sastrugi. Many places have been scoured down to dirt or old sun crusts. Warm temperatures on Monday created breakable crusts even on northerly aspects at middle and lower elevations. Be cognizant of these difficult conditions as you head out into the backcountry and remember that you could also still trigger a wind slab in wind loaded terrain. 

Wind slabs and variable snow conditions remain our primary concerns, but we are still tracking the weak layer of facets at the bottom of our snowpack on NW-N-E aspects at middle and upper elevations. These facets are buried 3+ feet deep by a stiff slab of snow, a recipe for deep persistent slab avalanches. The facets have mostly been unreactive in snowpit tests, yet propagation saw tests have still shown some potential for propagation. We have not received any reports of recent avalanches on these basal facets, but it is important to remember that deep persistent slab avalanches are very hard to predict and can stick around for much longer than other avalanche problems. If you found just the right spot, you could potentially trigger one of these avalanches, but it is highly unlikely.

recent observations

Variable snow surface conditions are present in the backcountry with a variety of hard and breakable crusts from recent sun, wind, and warm temperatures. 

Unreactive basal facets are buried 3+ feet deep on NW-N-E aspects on middle and upper elevations.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 27 deg. F.
Max. temperature in the last 24 hours: 29 deg. F.
Average wind direction during the last 24 hours: NE to WSW
Average wind speed during the last 24 hours: 5-15 mph
Maximum wind gust in the last 24 hours: 25 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 95 inches
weather

Ahead of a small incoming storm, clouds and westerly winds will increase through the day today. The storm will mostly pass by to our north tonight through tomorrow night. Expect minimal snowfall accumulations and strong westerly winds tomorrow. Warmer and calmer weather is forecasted for Sunday through Tuesday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Thursday Thursday Night Friday
Weather: Sunny then becoming mostly cloudy. Mostly cloudy then becoming partly cloudy. Mostly cloudy then becoming partly cloudy. Slight chance of snow in the morning.
Temperatures: 34 to 42 deg. F. 21 to 26 deg. F. 33 to 41 deg. F.
Wind direction: West Southwest Southwest
Wind speed: Light winds becoming west 15 to 25 mph with gusts up to 45 mph in the afternoon. 15 to 35 mph with gusts to 60 mph. 15 to 35 mph with gusts to 60 mph.
Expected snowfall: 0 in. 0 in. 0 to Trace in.
For above 10000 ft.
  Thursday Thursday Night Friday
Weather: Sunny then becoming mostly cloudy. Mostly cloudy then becoming partly cloudy. Mostly cloudy then becoming partly cloudy. Slight chance of snow in the morning.
Temperatures: 28 to 34 deg. F. 17 to 22 deg. F. 25 to 33 deg. F.
Wind direction: West Southwest Southwest
Wind speed: 15 to 30 mph. Gusts up to 45 mph increasing to 60 mph in the afternoon. 30 to 50 mph with gusts to 70 mph. 25 to 40 mph with gusts to 65 mph.
Expected snowfall: 0 in. 0 in. 0 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.