Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Fri
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

While avalanche activity remains unlikely today, variable snow surface conditions and increasing winds could present backcountry travel challenges. Avalanche danger will increase quickly as a storm brings new snow and wind to the region. Expect elevated avalanche danger tomorrow. Travel with normal caution in the backcountry today and watch for changing conditions. The avalanche danger is LOW today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Triggering an avalanche remains unlikely on a regional scale today. As new snow and wind begin this afternoon, the avalanche danger will start to increase. The 1 or 2 inches of new snow forecasted for today should not be enough to overload the snowpack, but wind drifted snow will start to form near ridgelines, in gullies, and on open slopes exposed to the wind. This drifted snow should not get deep enough to cause problems today, but it will represent the beginnings of wind slabs. The wind slabs will continue to grow during the night as more snow and wind impact the region. By tomorrow they could be a serious avalanche problem. Wind slabs could form sooner if the storm speeds up and more snow accumulates than forecasted this afternoon.

Avalanche Discussion

Today should remain quiet from an avalanche perspective. This will change as a winter storm brings new snow and wind to the area during the next 24 hrs. This storm will create avalanche problems for tomorrow including the wind slabs mentioned above and maybe some storm slabs. Some small wet snow instabilities may form on some lower elevation slopes if they get rained on today or tonight. It is unlikely that the storm will add enough weight to the snowpack to reactivate the more deeply buried weak layers like the Jan 22 crust/facet combo or the Dec 11 facets. 

Practice normal caution while traveling in the backcountry today.  Keep communication open with your group as you travel and discuss conditions and travel options throughout the day.  If your group sees signs of unstable snow or conditions that might exceed your abilities step back by switching aspects, decreasing slope angles, or moving to a more conservative option. Strong winds and variable snow conditions ranging from wind scoured slopes to rain crusts to patches of soft snow could make travel interesting today. 

Recent Observations:

* Yesterday observers found variable snow surfaces ranging from breakable rain crusts to warm wet snow to wind-scoured and sculpted snow to some softer snow.

* Observations from Mt. Lola (LIttle Truckee Summit area) and snowpit data and observations from Tragedy Springs (Carson Pass area) and Monument Canyon (south of Heavenly) all did not find signs of significant instability. Tests targetting the deeply buried old weak layers showed continued strength gains in those layers. 

*  Observations and snowpit data across the region continue to show strength gains throughout the snowpack. The late January storm snow has bonded well and continues to settle and gain strength.  The majority of data indicates that the old deep weak layers in the lower portion of the snowpack have gone dormant in most places. In a few isolated areas with a very weak and shallow snowpack, isolated unstable snowpack tests results continue.  The last know deep slab avalanche occurred 8 days ago on Feb 2.  

Regions covered