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

Continous strong SW winds have formed slabs of wind drifted snow that the weight of a person could still break on many leeward facing slopes in near and above treeline terrain. As more snow accumulates tonight, expect larger and easier to trigger wind slabs to form. MODERATE avalanche danger exists near and above treeline with LOW avalanche danger below treeline.

Problèmes avalancheux

  • Wind Slabs

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

    The strong SW winds continue to drift snow onto the leeward NW-N-NE-E-SE aspects. This continuous wind-loading has not given these slabs of wind drifted snow the chance to bond to the old snow below them. Human-triggered wind slab avalanches will remain possible today. In most areas, these wind slabs should remain small and may only knock a person off balance (D1). In the areas where more snow accumulated recently (like Donner Summit), they could involve enough snow to bury or injure a person (D2). As more snow starts to fall tonight, these wind slabs will become easier to trigger, more widespread, and larger in size. Large fragile cornices also exist along ridgelines across the forecast area.

    Stay alert for areas where possibly unstable wind slabs may exist by looking for clues like cornices above a slope, drifted snow, scoured ridges with smooth snow on one side, and wind-created surface textures. Use this information to plan travel routes with safety margins that appropriately manage this potential hazard. 

    D2 wind slabs on Mt. Judah that likely occurred on Jan 11. 

Avalanche Discussion

* Strong winds and blowing snow were reported across the forecast area. Observers in the Donner Summit area noted new cornice formation and wind slab growth. Large cornices above wind loaded slopes were also reported along the Mt. Reba Ridge near Bear Valley. 

* A few D1 and D2 skier and cornice triggered wind slab avalanches have occurred in the last 2 days in the Donner Summit (ob 1 and ob 2) and Echo Summit areas.

* Weak snow (facets) still exists below the Jan 4 rain crust. This layer varies in burial depth and strength around the forecast area, In many places, tests on this layer have indicated that it may fail under a significant new snow loading event like what is expected on Wed and Thursday. 

Régions couvertes