Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

New snow and wind will make avalanches more likely today, especially near ridges, in gullies, and on windy slopes where wind-blown snow accumulates. Avalanches may also be possible on steep, sheltered slopes where the new snow piles up too fast. It will take constant effort to carefully reassess the snow and terrain as you travel in today's rapidly changing conditions. 

Avalanche problems

  • Wind Slabs

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

    Gale-force winds and new snow will load snow onto leeward slopes near ridges, gullies, and wind-exposed slopes. This wind-blown snow will likely form wind slabs faster than it can bond to the snow below it. Triggering a wind slab avalanche will be likely today. These wind slabs may start small, but they will increase in size and extent quickly as new snow accumulates during the day. Wind slabs could grow large enough to bury or injure a person today. 

    Recent avalanche activity, blowing snow, cornices above a slope, cracking in wind-blown snow, and wind drifts can all help identify where unstable wind slabs may be growing. Use these clues to plan routes around the wind-loaded areas.  Don't assume that if a slope was fine an hour ago, it is still ok. Conditions will change quickly today. The same slope may go from only having a small amount of wind-blown snow in the morning to holding a wind slab large enough to bury a person in less time than it takes to have lunch. 

    (12/3/2024)

    A wind slab avalanche from earlier this season. This wind slab avalanche likely failed on 11/23/24

    Photo: Sierra Avalanche Center

  • Storm Slabs

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

    The forecast calls for the new snow to accumulate quickly today. It may pile up faster than it can bond to itself or the snow below it. Changes in temperature and snowfall rates during the storm may also create temporary weaknesses in the storm snow. These rapid changes may make it possible to trigger avalanches within the storm snow on steep, sheltered slopes today. Many of these storm slab avalanches could remain small, especially in areas that receive less new snow. Some of them could grow large enough to bury a person in areas that receive the high end of forecasted snow amounts or where terrain traps magnify the consequences of an avalanche.

    Recent avalanches, cracking in the storm snow, or feeling soft snow below more dense snow can indicate that ingredients for an unstable storm slab exist. Don't assume things will stay constant today; continuously assess the snow and terrain as you travel. If you see signs of unstable snow or have doubts about a slope, reassess and move on to a different area. 

    (1/15/2023)

    This is an example of a storm slab avalanche from 2023. Storm slab avalanche triggered in NE aspect, below treelin terrain, at about 8,300'. Rubicon Peak, West Shore Tahoe, CA

    Photo: Public

Avalanche Discussion

The Dec 12 persistent weak layer and basal facets continue to exist in the southern and eastern portions of the forecast region. These areas are mostly above 8000-8500' and in locations with a shallower and weaker snowpack. Some snowpit tests continue to produce unstable results in isolated areas, but most data indicates that these weak layers have gained strength and can support the current snowpack. While today's new load may not be enough to reawaken these layers, larger loading in the future may still have the potential to reactivate them. 

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