Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
1 · Low
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 13 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Near treeline and below treeline, MODERATE avalanche danger continues on NW-N-NE aspects on slopes 32 degrees and steeper due to lingering persistent slabs.

Human triggered avalanches remain possible. Shallow covered rocks, logs, and stumps are an additional hazard to backcountry travelers. Impact with rocks or trees while caught in an avalanche can greatly increase consequences.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    It is now two weeks past the most recent significant snowfall event and persistent slab instability continues. While some small and very gradual improvement in stability has occurred over that time, it is fairly negligible in the big picture. The problematic Dec 7 persistent weak layer remains widespread in NE wind protected areas near treeline and below treeline on NW-N-NE aspects. Obvious clues of instability are still encountered on a near daily basis by backcountry travelers. Snowpit data remains very telling of the current instability. Venturing into steep terrain where this weak layer exists beneath an overlying slab is begging to trigger an avalanche.

Avalanche Discussion

Observations made yesterday on the East Ridge of Tamarack Peak (Mount Rose backcountry) fell right in line with previous observations made around the forecast area over the past two weeks. Persistent slab instability continues near treeline and below treeline on NW-N-NE aspects. In these areas, the faceted Dec 7 persistent weak layer is barely able to support the overlying slab of cohesive snow. Once the additional weight of a person is added to the snowpack, collapse of the weak layer has frequently occurred. This is clearly seen in snowpit tests on a regular basis, in addition to the human triggered collapsing, whumphing, and cracking that is still experienced in some areas. Yesterday's NE ridgetop winds were once again observed to scour snow from above treeline areas on N-NE aspects.

Rocks, logs, and stumps lurk below the snow surface. The ability of the snowpack to keep a person supported above these hazards remains variable and can change greatly over short distances. Travel accordingly to minimize the risk of injury.

Regions covered