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

Early this morning, avalanche danger is LOW for all elevations and aspects. Areas of MODERATE avalanche danger will form at all elevations and on all aspects on slopes 35 degrees and steeper as loose wet avalanche problems develop in response to daytime warming.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    With clear skies and below freezing air temperatures, a strong snow surface refreeze will have occurred last night. The exception will be in the areas along the Sierra Crest in the northern portion of the forecast area where several inches of storm snow accumulated Wednesday night. In these areas a thin breakable crust will exist on top of recent storm snow that has yet to be affected by melt-freeze. This remnant storm snow sits on top of hard melt-freeze crust. In areas that received little to no new snow this past week or were wind scoured yesterday, expect hard melt-freeze crust at the snow surface

    As daytime warming occurs, snow surface melt is expected to today. Melt will occur mainly on E-SE-S-SW-W aspects with some degree of melt occurring on NW-N-NE aspects as well. Areas with remnant storm snow on the surface and direct sun exposure will be the most prone to loose wet avalanches today.  Areas with melting crust will become unstable once the surface crust looses supportability.

    In areas with recent new snow, roller balls, pinwheels, and test slope failures will be the indicator that unstable wet snow is developing. In areas without recent storm snow, body weight boot penetration into surface wet snow will be the indicator. Boot penetration of 8 to 10 inches or more is problematic. When signs of wet snow instability are present, exit avalanche terrain by moving onto slopes less than 30 degrees in slope angle without steeper terrain above.

Avalanche Discussion

Observations made yesterday on Castle Peak (Donner Summit area) revealed unstable wet snow in sun affected areas and blowing snow along the ridgetops. At noon, ski cuts on steep E aspect micro terrain features within a macro scale S aspect produced small loose wet avalanches. These avalanches involved all of the 4 inches of recent storm snow and ran on the hard melt-freeze crust below it. Areas of blowing snow were visible all along the Sierra Crest in the Donner Summit area, but new wind slab formation was minimal.

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