Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Areas where wind drifted snow has deposited into a cohesive slab near ridgelines remain the main avalanche concern for today. Gradual, incremental loading of new snow onto a very weak snowpack will increase concern for avalanches in wind protected areas over the next 24 hours. Travel with caution today. The snow cover is thin and shallow with many obstacles to hit.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    The combination of new snow and wind over the last 36 hours created slabs of denser snow along the downwind side of ridgetops. Drifting and depositing of new snow is expected to continue today and tonight, keeping this avalanche problem ongoing. In some areas, wind slabs may exist on top of a very weak, sugary (faceted) snowpack. Triggering lower on the slope than is common for a wind slab avalanche could easily occur anywhere a slab exists on top of a weak, faceted snowpack.

    Use clues such as visible drifting snow, cornice formations, wind pillows, or other signs of snow distribution on the ground to identify areas that hold wind slabs. Exercise increased caution around areas where wind drifted snow has been deposited.

     

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–2

    Gradual, incremental loading of new snow onto a very weak snowpack is raising the concern for a persistent slab avalanche problem to develop mainly on NW-N-NE aspects. In more isolated areas, weak faceted snow also exists on E and W aspects. New snow amounts over the next 24 hours could load up to another 0.5 inches of SWE on top of the recent snow load of 0.2 to 0.4 inches of SWE that occurred Thursday night. There is a high amount of uncertainty here. With relatively smaller, incremental loads added over a few days, it is hard to know when the breaking point for the snowpack will occur.

    Any snowpack collapses, whumpfing sounds, or shooting cracks encountered are signs of an unstable snowpack. If you are encountering any of these signs of instability, avoid NW-N-NE aspect avalanche terrain in the area.

Avalanche Discussion

Throughout the forecast region, 1 to 2 feet of snow can be found on NW-N-NE aspects above 8000'. Continuous snow cover starts around 7,400' to 8,000' depending on location. The snowpack on NW-N-NE aspects is either rain crust under new snow, a mix of rain crusts and faceted snow, or all faceted snow and depth hoar depending on location and elevation. The presence of rain crusts generally decreases as elevation increases.

Previous NE wind events scoured the upper portion of many wind exposed slopes down to rock, dirt, and/or ice before the recent snowfall.  Snow coverage and snowpack structure are highly variable throughout the forecast region. A much thinner snowpack or bare ground exists across E-SE-S-SW-W aspects.

Early season conditions exist with many obstacles (rocks, bushes, logs, open water, etc.) exposed or barely covered. Hitting one of these hazards could easily end your season before it even begins.  If you are traveling on snow for recreation, you should come up with a daily travel plan based on the current conditions and associated hazards.

Regions covered