Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Tue
Alpine
1 · Low
Treeline
1 · Low
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Out of date — this forecast expired 3 years ago.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

Isolated areas of unstable snow may exist where the deepest pockets of wind-drifted snow formed on Saturday, especially in shaded terrain. Travel with a mindset and actions that will minimize the consequences of triggering an unexpected avalanche. This forecast will be updated on January 2nd.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–1.5

    Saturday's storm underperformed with new snow amounts. For the most part, wind slab formation reported Saturday was small and unreactive. Keep an eye out for any areas where 4+ inches of new snow drifted in on top of weak faceted snow at the old snow surface or onto thin, breakable crusts at the old/new snow interface. If a wind slab avalanche is triggered today, it will likely be on this setup.

    Identify areas where wind-drifted snow was deposited onto NW-N-NE-E aspects that held weaker snow at the old snow surface, especially in shaded areas. Cornices, wind drifts, and snow surface texture are helpful indicators of potentially suspect areas. If it appears that a 4+ inch thick slab drifted in on top of weaker snow below it, consider choosing different terrain.

    (12/30/2023)

    Terrain with signs of recently wind drifted snow. Mt Judah, Donner Summit area, CA

    Photo: SAC

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–2.5

    Upper elevation NW-N-NE aspect terrain above about 8500 ft holds layers of weak faceted snow near the ground buried 1 to 3 feet below the old snow surface.  This weak layer appeared to have become dormant leading up to Saturday's snowfall. Generally speaking, the amount of new snow that fell on Saturday should be insufficient to reactivate this weak layer.

    There is a very slight chance that in some isolated location exposed to very efficient wind loading, enough snow drifted in causing this deeper weak layer to reactivate. Any persistent slab avalanches that occur will have a high-density slab and probably expose rocks and logs at the bed surface, both of which will increase the likelihood of trauma.

    Any signs of snowpack collapse or whumpfing sounds are indications that this avalanche problem is reactive. Be wary of any wind-loaded areas where 8 to 12+ inches of snow drifted in across NW-N-NE aspects near and above 8,500'. Consider avoiding any areas where these specific set of circumstances exist. The likelihood of encountering this amount of wind-drifted snow is quite low, but the consequences of triggering could be substantial.

Avalanche Discussion

The snowpack is usable, mainly on NW-N-NE-E aspects above 7,500 to 8,300 ft depending on location. Periods of melt have caused the lower limit of the usable snowpack to creep upwards in elevation. Expect some rocks to hit and open creeks to deal with.

Regions covered