Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 7 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Wind slab avalanche problems will keep the avalanche danger at MODERATE in near and above treeline terrain today. Human-triggered avalanches large enough to have consequences are possible. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    Slabs of wind drifted snow exist on leeward aspects (NW-N-NE-E-SE) in near and above treeline terrain. Where more new snow has accumulated in the last 24 hours, more fragile wind slabs may exist. In areas where older wind slabs exist, they should be more difficult to trigger. Complex or extreme terrain including couloirs, cliffy areas, unsupported slopes, and steep convex rollovers will be the most suspect. Wind slab avalanches could entrain enough snow to bury, injure, or kill a person. Large cornices also exist along exposed ridgelines.

    Identify where problematic wind slabs may exist by looking for cornices above a slope, blowing snow, drifted snow, and other wind created surface textures. These areas will have more avalanche concerns and more variable and challenging snow conditions. On the other hand, areas sheltered from the wind should have fewer avalanche concerns and softer more consistent snow conditions.

Avalanche Discussion

* Yesterday observations from near Ebbetts Pass, on Luther Pass, and on Donner Summit found wind slabs on wind-loaded slopes with a layer of lower density snow below them. Snowmobile cuts and ski cuts on previously undercut wind-loaded tests slopes caused some shooting cracks or test slope failures. Ski and snowmobile cuts on non-undercut slopes did not produce signs of instability. Other tests and observations indicated that these wind slabs are becoming more difficult to trigger, but some snowpit tests still produced unstable results. 

* Large cornices existed above many wind-loaded slopes.

* Observations and data from sheltered slopes in these areas did not show lingering signs of storm slab instability. 

Régions couvertes