Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

MODERATE avalanche danger will exist today in most portions of the forecast area at all elevations. CONSIDERABLE avalanche danger may develop near treeline and above treeline in any areas that receive close to or more than a foot of new snow. Wind slabs are the main avalanche problem of concern. Isolated storm slabs may form in the areas of greatest new snow accumulation. Factor in how decreasing snow stability will affect travel plans and terrain selection as the day progresses.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    New wind slabs are expected to form this morning as SW winds drift new snow onto NW-N-NE-E-SE aspects in near treeline and above treeline terrain. Additional wind slab development is expected to occur this afternoon and evening with continued wind and snow showers. Avalanche size up to D2 (large enough to bury or injure a person) is possible today.

    Identify and avoid areas of potentially unstable wind slab by looking for newly wind drifted snow. Slopes near or adjacent to a recent avalanche or those that have cornice features or wind pillows across the upper portion of the slope are the most suspect. Areas of snow surface cracking in near treeline and above treeline locations are an additional indication of unstable snow.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    This avalanche problem will be specific to areas that receive the upper end of forecast snowfall amounts of around a foot by this afternoon or evening. This problem will be unlikely on a regional scale today, but could be an issue in isolated areas.

    Isolated storm slabs could become a problem today or tonight in wind protected areas below treeline that held snow cover prior to the current storm. This is mainly NW-N-NE-E aspects at the mid and upper elevations with very isolated distribution on all other aspects. This problem will be dependent on the formation of a weak layer within the storm snow that is deposited today. The period of snowfall at 2 inches per hour that is expected this morning followed by the second round of snowfall this afternoon and evening will be conducive to this type of potential weak layer formation. Avalanche size of D1 is most likely with size D2 possible in any areas that receive close to or more than a foot of new snow.

    Avoid steep terrain in below treeline areas where any signs of instability have been observed. Human triggered snow surface cracking and/or recent avalanches are the easiest to identify signs of unstable snow.  

Avalanche Discussion

* In most areas, the existing snowpack is in good condition to handle new snow loading. The one indication of exception to this was observed in the Carson Pass area on NE aspects between 8,600' and 8,800'. Around 1 foot or less below the old snow surface in this area, a thin crust with layers of faceted snow above and below it gave indications of a potentially problematic weak layer under new snow loading conditions.

* Snow cover remains thin at the lower elevations on all aspects and on most but not quite all mid and upper elevation SE-S-SW-W aspects. Mid and upper elevation NW-N-NE aspects hold a much deeper snowpack.

Regions covered