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

Avalanche danger has risen to CONSIDERABLE for areas above 8,000' near and above treeline on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper. For all other areas, avalanche danger is MODERATE on slopes 35 degrees and steeper. Human triggered avalanches are expected today. Don't let the desire for powder negatively affect sound decision making. Specifically choosing slopes based on slope angle will be the difference between "getting lucky" and "getting it done" in the backcountry today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Above 8,000', newly formed wind slabs exist on NW-N-NE-E-SE aspects and potentially in isolated areas on other aspects as well. Gale force winds throughout the period of snowfall will have created wind slabs in just about any lee areas both above and below treeline. Rising snow levels during the event will have deposited increasingly high density snow on top of (relatively) lower density snow creating an opportunity for slab over non-persistent weak layer formation. Slab depths of 2 to 4+ feet are possible today in heavily wind loaded areas. Ongoing human triggering of these wind slabs is expected today with avalanche size easily large enough to bury and/or injure a person.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    In areas of protection from ongoing SW winds, storm slabs are possible above 8,000' on all aspects where new snow was deposited on top of an old snow bed surface. Rising snow levels will again have created the potential for slab over non-persistent weak layer formation. Human triggered avalanches will remain possible today in wind protected areas both near and below treeline with slabs depths of 6 inches to 1.5 feet. Some of these storm slabs may present with wet slab characteristics.

Avalanche Discussion

Recent observations from around the forecast area including those made yesterday on Tamarack Peak (Mount Rose area) indicated that the existing snowpack was in good condition to handle the new loading from rain and snow received over the past 18 hours. Rain and melt freeze crusts that exist at or just below the old snow surface are strong and supportable. Softer layers of rounding facets and rounded snow grains below these crusts have given no indication of holding the proper characteristics to support propagation upon collapse. Avalanche activity from last night and ongoing instability today are expected to occur at or above the old/new snow interface.

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