Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

New snow and strong winds will create slabs of wind drifted snow in exposed areas below ridges and gully features.  In areas that received the higher end snow totals, weaknesses may exist in the new storm snow which may prevent it from bonding and gaining strength.  Dangerous avalanche conditions will exist today with human and natural avalanche activity expected. 

Avalanche problems

  • Storm Slabs

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

    Up to another foot of additional storm snow has fallen in the last 24 hours on top of the previous storm snow from Tuesday night.  Cold temperatures will slow down the bonding and settlement process of this new storm snow.  Many different snow precipitation types have fallen including multiple layers of graupel.  Any of these different layer types may be problematic and not bond well to the additional snowfall expected.  More rapid snowfall rates expected in some locations later today may also overload the existing new storm snow layers.  Areas that have received the upper end of new snow totals will be the most concerning for storm slab avalanches.

    Natural and human triggered avalanches could occur today in near and below treeline areas.  Look for snow surface cracking or any indication that weakness and cohesion exist in the new storm snow.  If unstable snow is encountered, move into lower angle non avalanche terrain with no overhead hazard. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Light density new snow along with gale force SW winds will build large wind slabs and cornices today.  These wind slabs will be most prevalent on NW-N-NE-E-SE aspects in near and above treeline areas, but could also form in other locations below treeline due to the strength of the wind.  Visibility will be very limited today in most wind exposed locations.  Human triggered and natural wind slab avalanches are expected to occur today along with cornice collapses.

    Slopes with cornices above and areas below ridges and in gully features will be where  a lot of this blowing snow will be deposited.  Route finding skills and familiar terrain will be key to avoiding this wind slab avalanche problem today.  Snow surface cracking is a sign of unstable snow in the area.  Avoid steep wind loaded terrain and areas below slopes with large cornices above.   

    (2/22/2023)

    Up to 12'' wind slabs cracking and small propagation from ski kick.  Incline Lake Peak, Mt. Rose area.

    Photo: SAC

Avalanche Discussion

Recent Observations:

  • Graupel (pellet snow) was noted during some of the storm on Tuesday afternoon 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.

Regions covered