Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Unstable slabs of wind drifted snow may exist near ridgelines and in gully features. Move carefully around areas where wind drifted snow has deposited, especially on slopes below or adjacent to cornice features. Avalanche danger is expected to further increase tonight and tomorrow as storms continue.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Strong to gale force winds out of the SW to W combined with 2 to 6 inches of new snow will have formed new wind slabs in the areas where wind drifted snow has deposited. Wind slabs exist mainly above treeline and near treeline on NW-N-NE-E-SE aspects. Smaller, more isolated wind slabs may exist below treeline in some locations due to the strength of the recent winds. It will be possible for backcountry travelers to trigger avalanches up to size D2 today.

    Identify the areas where blowing and drifting snow has accumulated into cohesive slabs. Slopes below or adjacent to cornices, areas along ridgelines, and cross-loaded gully features are areas of concern for unstable wind slabs. Identify and move cautiously around areas where wind slabs have formed. Snow surface cracking is a sign of unstable snow in the area. Choosing wind sheltered terrain is a strategy for reducing the chances of encountering this avalanche problem.

    (2/14/2023)

    An example of snow surface cracking on a small test slope. Move cautiously around wind loaded terrain near any areas where this is occurring.

    Photo: SAC

Avalanche Discussion

Recent Observations:

  • Graupel (pellet snow) was noted during much of the early part of yesterday's snowfall and may contribute to instability as a potential weak layer today.
  • Melt-freeze crust exists below the recent new snow across most E-SE-S-SW-W aspect terrain. 
  • Some layers of old graupel, facets, and/or buried surface hoar can be found about one to two feet below the snow surface on some NW-N-NE aspects. For the most part, these layers are well bonded into the snowpack. It is unlikely that the amount of low density new snow load that occurs this week will overload these layers.

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