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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Out of date — this forecast expired 12 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

CONSIDERABLE danger exists on slopes 35 degrees and steeper on wind loaded NW-N-NE-E-SE aspects in near and above treeline terrain. MODERATE avalanche danger exists in all other areas. Human triggered wind slab avalanches are likely today and storm slab avalanches are possible.

After 2 weeks of stable melt-freeze conditions, today represents a day when natural and human triggered avalanches could occur. Don't let excitement over the return of winter and/or "powder fever" override good judgment and thoughtful and safe backcountry decision making.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Human triggered wind slab avalanches are likely today and natural wind slab avalanches may become possible. New snow and southwest winds created new wind slabs on the wind-loaded aspects last night. As the snow and wind continue today these wind slabs will become more widespread and larger. In exposed near and above treeline terrain, fragile wind slabs 2 to 3 ft in depth could exist on the wind loaded N-NE-E aspects and cross loaded NW and SE aspects by this afternoon. In areas where more or less snow falls than forecasted the winds slabs could either be larger or smaller.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Human triggered storm slab avalanches will become possible today due to an increase in snowfall intensity and fluctuating snow levels. This combination will allow heavier layers of storm snow to form above lighter layers of storm snow. In addition the changing conditions during the storm could also allow other storm snow weakness to form within the storm snow. The easiest places to trigger these storm slabs will be on the sheltered northerly aspects above 8000 ft. that held thin breakable crusts prior to the storm, but fragile storm slabs resting on firm crusts could exist on any slope that had previous snow cover.

Avalanche Discussion

Observations on Becker Ridge yesterday remained consistent with data collected from around the region during the last 10 days. Stable melt-freeze conditions existed on the southerly aspects, and a well consolidated snowpack existed on the northerly aspects. The observations and data did not indicate lurking instabilities below the surface of the old snow. However, the surface conditions that consisted of a myriad of smooth crusts, scoured surfaces, and some thin breakable crusts with soft snow just below them could represent great bed surfaces for avalanches to run on and/or surfaces that may be difficult for new snow to bond with.

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