Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Additional human triggered wind slab and storm slab avalanches occurred yesterday. Avalanches remain possible today both above and below treeline due to continued deposition of wind drifted snow (wind slabs) and slow to bond recent new snow (storm slabs). MODERATE avalanche danger exists for all elevations.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Natural and human-triggered wind slab avalanches were reported both Friday and Saturday and remain possible today. Ridgetop winds and drifting snow continued after the end of snowfall yesterday. Additional drifting snow is expected today, keeping this avalanche problem ongoing. Slabs of wind drifted snow exist on leeward slopes near ridgelines, in gullies, and on open slopes exposed to the wind. Some of these slabs may have formed in atypical places due to the wind shifting between SW and NW. Today's wind slabs could measure 1 to 3 feet in depth and could easily involve enough snow to bury or injure a person.

    Clues like recent wind slab avalanches, cornices above a slope, blowing snow, snowdrifts, ripples on the snow surface, and other wind created features can be used to identify where wind slabs exist. Move around areas of suspect wind slab with caution, giving them a wide berth. Cornices were fragile yesterday and may remain fragile today.

    (2/13/21) Incline Peak, NV wind slab crown. Note the ripples on the surface indicative of wind drifted snow.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    A second round of storm slab avalanches occurred yesterday, though not as widespread as on Friday. Recent new snow has been slow to bond allowing for a low end possibility of continued storm slab avalanches occurring today. Storm slab avalanches could involve enough snow to bury or injure a person. This avalanche problem exists in places that people gravitate towards to avoid wind slabs such as wind protected, tree-covered slopes. In these cases, avalanches could have more severe consequences if they push people into trees or other obstacles. Terrain traps such as narrow gullies and creek beds can also magnify the consequences of a storm slab avalanche via deeper burial.   

    Recent avalanche activity, shooting cracks, or dense over soft feeling snow, are clues to storm slab instability. If these clues are present, move to sub 30 degree slope angle terrain.

    (2/12/2021) Skier triggered avalanche on Flagpole Peak. This skier was carried for some distance and then able to self-arrest.

Avalanche Discussion

Numerous natural and human triggered avalanches occurred Thursday night, Friday, and to a lesser extent on Saturday. Some were wind slabs, many were storm slabs. Crown heights measured ~1 ft on Friday and 1 to 2 ft on Saturday for the storm slabs and 1 to 2 ft for the reported wind slabs on both days. These avalanches occurred on steep slopes on N-NE-E-SE-S aspects.

There were two reported incidents on Friday in which the person who triggered the avalanche was also caught and carried by it. One on Flagpole Peak (reported as a storm slab) where the person lost a ski but was otherwise unharmed, and one in the Blue Lakes area (likely a wind slab) where the person was fully buried and suffered serious injuries.

Régions couvertes