Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Triggering avalanches in areas where wind-blown snow piles up may be possible today. Most of these would remain small, but some could be large enough to cause problems. Watch out for open slopes where wind-drifted snow exists.

Problèmes avalancheux

  • Wind Slabs

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

    New snow and strong winds will pile snow onto leeward aspects today. Even though new snow amounts may seem small, wind-loading can increase snow depths by several times in areas where wind-blown snow accumulates. Wind slabs could exist on almost any aspect today due to strong winds from both the SW and NE. Open slopes exposed to the winds in near and above treeline terrain represent the most likely places to find wind slabs. Most of these should remain small and not extend very far from the ridges, but some wind slabs may grow large enough to cause problems for backcountry travelers in the most wind-loaded areas or in areas that receive the most new snow. In areas that receive less snow, wind slabs will be smaller and more isolated. 

    Look for clues like blowing snow, cornices above a slope, wind-created surface textures, and smooth hollow-sounding snow to help identify where wind slabs might exist. Recent avalanches or cracking represent sure signs that wind slabs are unstable. Identifying areas where triggering a wind slab may be possible can help avoid an unpleasant surprise while you recreate in the snow. Areas sheltered from the winds will hold more consistent and less wind-affected snow. 

Avalanche Discussion

  • Snowmelt has sped up over the last two weeks exposing more obstacles (rocks, bushes, etc) and areas of bare ground on SE-S-SW aspects.
  • Under today's new snow, highly variable old snow surfaces exist including smooth firm surfaces, rough uneven surfaces, soft weak snow, melt-freeze crusts, and everything in between. 
  • Gradual near-surface faceting has created weak snow in the top portion of the snowpack on many wind-protected and semi-wind protected NW-N-NE aspects. Today's new snow will bury this weak layer but should not add enough load to break it in non-wind-loaded areas. 

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