Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Considerable avalanche danger exists at all elevations due to wind slab and storm slab avalanche problems.  Dangerous avalanche conditions exist.  Natural triggered avalanches are possible and human triggered avalanches are likely.  Cautious route finding and conservative decision making are essential today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1

    Wind slabs started to develop quickly yesterday by mid day as new snow and gale force SW winds moved into the forecast area.  These wind slabs have grown in size overnight and will continue to increase in size through the morning.  Winds slabs are expected on NW-N-NE-E-SE aspects in near treeline and above treeline terrain.

    Look for blowing snow, cornice formation, wind pillows, and snow surface clues as to where wind slabs exist.  Avoid recently wind loaded terrain.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Storm slabs will be possible on all aspects in near treeline and below treeline terrain today.  Many areas throughout the forecast area have received 12'' of new snow with more snow forecasted this morning.  A rise in temperature during the storm last night before cooling back off may have contributed to an upside down storm snow structure.  In some areas, this new storm snow may have fallen on existing near surface facets or surface hoar.

    Signs of storm snow instabilities could be snow surface cracking, snow collapsing, and whumpfing.  Avoid slopes steeper than 30 degrees in areas where signs of unstable storm slabs are present.

Avalanche Discussion

Observations were made and received yesterday from Castle Peak (Donner Summit area) and Elephants Hump (Carson Pass area).  Wind slabs were forming and reactive by late morning on Castle Peak.  Strong to gale force winds were moving snow along exposed areas as the storm came in earlier than forecasted.  On Elephants Hump, the old snow surface consisted of a variety of crusts and wet snow.  Both areas showed relatively good bonding with the new snow to the existing snow surface.

Regions covered