Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Moderate avalanche danger will exist today with wind slab and persistent slab avalanche problems.  Human triggered wind slab avalanches will be possible in near and above treeline terrain.  Persistent slab avalanches will continue to be possible at all elevations.  Areas of concern exist on specific terrain features, evaluate snow and terrain carefully.  Avalanche danger is expected to rise with the approaching storm on Monday.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Newly formed wind slabs yesterday could remain sensitive today on NW-N-NE-E-SE aspects in near and above treeline terrain above 8500'.  Increasing SW winds this afternoon could form new wind slabs and add weight to existing wind slabs.  In isolated areas, wind slabs may be on top of old near surface facets on NW-N-NE aspects.  Look for cornice formation, blowing snow, and signs of previous blowing snow, especially along ridgelines and wind exposed areas.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Yesterdays storm added significant rain and heavy snow to the layer of weak faceted snow that exists below the snow surface.  In some areas, these facets have gained strength from being wetted from the recent rain and heavy snow.  In high elevation areas and places that the facets are protected by an overlying slab, these facets remain dry and loose in many locations.  This faceted layer is still producing unstable snowpack test results along with cracking in isolated areas.  

    Avoid steeper slopes in areas where snow surface cracking, whumpfing, and/or unstable snowpit test results are occurring.  Quick hand pits remain an effective tool for seeing if a slab over weak faceted snow exists.

Avalanche Discussion

* Natural wind slab avalanche reported off of Elephants Back (Carson Pass area) yesterday.

* Natural D2 loose wet avalanche reported off of Twin Peaks (Ward Canyon area).

* Reports of wind slabs failing on old near surface facets in the Carson Pass area and Mt. Rose area.

* Where faceted snow exists under a slab, the facets continue to remain dry and reactive in snowpit tests.

* NW-N-NE aspects above 8,000' in the Mt. Rose area and along the Sierra Crest north of Emerald Bay hold the best snow coverage at 2 to 3+ feet. Overall less snow cover exists south of Emerald Bay. Areas of decent coverage exists above 8,500' on NW-N-NE aspects in the Carson Pass area.  Coverage decreases on all other aspects. Large areas of bare ground exist on the vast majority of southerly aspects at all elevations.

Up to 2'' of rain has fallen throughout the forecast area below 8500'.  The snow surface in these areas are expected to refreeze overnight and into this morning creating firm rain crusts on all aspects below 8500'.  Some softening is expected throughout the day as temperatures warm.  Roller balls could occur on E-SE-S-SW aspects depending on the amount of sun we receive today.  Larger loose wet avalanches are not expected today.  

Regions covered