Snowpack Summary published on March 20, 2021 @ 8:06 am
Issued by Jason Mozol - Bridgeport Avalanche Center

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Human triggered avalanches are likely following recent rain and snowfall. Strong winds formed wind slabs in near and above treeline terrain; storm slabs persist in sheltered areas. Wet loose instabilities will increase in sun exposed areas as clouds dissipate. Today is a good day to practice avoidance by sticking to non-avalanche terrain instead of managing complex, overlapping avalanche problems.

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.

Wind slabs formed in exposed terrain such as alpine areas along the Sierra Crest and near treeline areas around Leavitt Lake from strong SW winds. These slabs will likely be dense and stubborn to trigger but produce large avalanches. Be on the lookout for any signs of recent avalanches as an indicator that conditions are unstable.

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.

Precipitation from the storm varied from fluffy, low density snow to wet, high density snow to rain and resulted in weaknesses within the layer of new snow. Yesterday, there was evidence of cracking in the storm layer and snowpit tests produced unstable, propagating results. Cracking or collapsing in the snow are common signs of unstable conditions.

Avalanche Character 3: 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.

The new snow fell wet and will not need much warming from the sun to produce loose wet avalanches. Once the sun breaks through the clouds or you take out the sunscreen, consider loose wet avalanches. Move to shaded areas when the surface snow is becoming saturated and unconsolidated.

Snowpack Discussion

Plan for wide safety margins with multiple avalanche problems present in the backcountry. Today's forecast comes with plenty of uncertainty due to rapidly changing conditions and a lack of recent field observations. You can help us gather these observations! Submit your photos or written reports here. Information about recent avalanches, the weather or how the riding was all help us produce a more accurate forecast.


Spring-like conditions return with clear skies and warm days on the horizon. Loose wet avalanches will become the primary concern. Avoid areas receiving lots of sun as it gets later in the day. We will also be keeping an eye out for signs of wet slab avalanches as water percolates through the snowpack and penetrates buried weak layers.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 15 deg. F.
Max. temperature in the last 24 hours: 32 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 20-40 mph
Maximum wind gust in the last 24 hours: 66 mph
New snowfall in the last 24 hours: 11 inches
Total snow depth: 113 inches

Light snow showers will give way to clearing conditions this afternoon. Winds will remain gusty from the W and temperatures will top out around freezing.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Saturday Saturday Night Sunday
Weather: Mostly sunny, isolated snow showers Partly cloudy, isolated snow showers Partly cloudy becoming sunny
Temperatures: 25-35 deg. F. 10-16 deg. F. 29-37 deg. F.
Wind direction: W N N
Wind speed: 15-20 mph, gusting to 30mph 15mph, gusting to 30mph Light with gusts of 15-20mph
Expected snowfall: Up to 1 in. Up to 2 in. 0 in.
For above 10000 ft.
  Saturday Saturday Night Sunday
Weather: Partly cloudy becoming sunny. isolated snow showers Partly cloudy to mostly cloudy. Isolated snow showers Mostly cloudy becoming sunny
Temperatures: 16-24 deg. F. 3-9 deg. F. 20-28 deg. F.
Wind direction: W N NE
Wind speed: 15-25mph gusting to 35mph Light, increasing to 15mph 15mph gusting to 30mph
Expected snowfall: Up to 1 in. up to 2 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.