Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You could trigger a large avalanche today, including in wind sheltered, below treeline terrain that is often viewed as safer terrain. Graupel (pellet snow) was observed at the start of the storm in many locations yesterday. If this graupel layer is reactive, wide propagating avalanches may occur, so consider avoiding avalanche terrain today. The density of the new snow should make for good recreation in non-avalanche terrain.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    The rapid accumulation of 1 to 2 feet of new snow on top of a graupel layer has given us the setup for a storm slab avalanche problem. In many locations, the graupel sits on top of crust at the old/new snow interface. In wind loaded areas, slab thickness of 2 to 4 feet is anticipated.

    A natural avalanche cycle may have occurred last night. Unstable slabs are expected to remain today. Backcountry travelers who venture into avalanche terrain today should anticipate an increased likelihood of triggering large avalanches. There is a chance that an avalanche that initiates in a wind loaded area could be big enough to break a few trees or challenge a perceived "safe zone".

    Avalanches could occur in either wind loaded or wind protected areas today across all aspects. Recent avalanches, test failures, or snow surface cracking are signs that unstable snow exists in your area of travel. The easy answer for managing today's avalanche problem is to choose lower angle, non-avalanche terrain, without connected steeper terrain above or to the side. Fun recreation can easily be had in non-avalanche terrain.

    Traveling in avalanche terrain today is taking on substantial risk. Consider avoiding terrain where it is not possible to expose only one person at a time to avalanche terrain, both while ascending or descending. Choose terrain with a minimum of down slope hazards to hit if the slope avalanches. Better yet, choose terrain not capable of producing large avalanches. Don't rely on marginal safe zones and don't go solo. It will be snowy and windy today. Helicopters won't be flying in the mountains, and SAR response will be delayed.

     

    Test slope failures like this one are a sure sign of unstable snow. This one was triggered back on Feb 13 on Mt. Judah, Donner Summit area, CA.

    Photo: Public

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