Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Blowing and drifting snow over the past 24 hours is keeping concerns for areas of unstable snow ongoing. Exercise caution in places where wind drifted snow has deposited as a cohesive slab, mainly on slopes near ridgetops and in gully features. Use clues such as blowing snow, wind sculpted snow surfaces, and snow surface cracking to help identify areas of concern.

Problèmes avalancheux

  • Wind Slabs

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

    Signs of unstable wind slabs were present yesterday and are expected to continue today. Ridgetop winds shifted from NW to NE late yesterday afternoon and remained plenty strong to blow and drift snow overnight. Unstable snow remains a concern in near treeline and above treeline terrain in places where drifting snow has deposited as a cohesive wind slab across SE-S-SW-W-NW-N aspects.

    Identify the slopes where blowing and drifting snow has accumulated and created potentially unstable wind slabs. Slopes near ridgetops as well as cross-loaded gully features have the greatest chance of holding unstable snow today. Exercise caution around areas of smooth looking snow that are surrounded by areas of rough, wind sculpted snow surfaces. Slopes where continued blowing snow is depositing are suspect. Snow surface cracking is a sign of unstable conditions. If in doubt, don't engage with slopes of concern. Wind protected slopes below treeline offer the potential to avoid this avalanche problem.

    (2/14/2023)

    Snow surface cracking on a wind loaded test slope. A sign of unstable snow. Elephants Hump, Carson Pass, CA.

    Photo: SAC

Avalanche Discussion

Recent Observations:

  • Snow surface cracking was reported as widespread yesterday on wind loaded test slopes in the Carson Pass area.
  • Unconsolidated snow, unaffected by previous melt lingers on shaded northerly aspects in wind protected terrain below treeline.
  • Melt-freeze crust exists on most sun-exposed slopes. 
  • About one to two feet below the snow surface, older weak layers of buried surface hoar, near-surface facets, and/or graupel remain in some areas. Observations indicate a trend of increasing stability on these layers with improved bonding and decreasing reactivity in snowpit tests.

Régions couvertes