Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 10 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Considerable avalanche danger exists at all elevations due to wind slab, storm slab, and deep slab avalanche problems.  Dangerous avalanche conditions exist.  Natural avalanches are possible and human triggered avalanches are likely.  Careful snowpack evaluation, cautious route finding, and conservative decision making are essential today.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2

    Very large wind slabs have formed on NW-N-NE-E-SE aspects in near treeline and above treeline terrain during our recent storm cycle.  These wind slabs will remain fragile today and grow in size with additional snow and wind.  As the wind direction changes from SW to NE/E today, wind slabs will also become possible on S-SW-W-NW aspects in exposed near treeline and above treeline terrain.

    Look for blowing snow, cornice formation, snow surface clues, and wind pillows as to where wind slabs are developing or have previously been developed.  Very large cornices exist along ridgelines, extra caution is advised around these hazards.  

  • Loose Dry

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

    Storm slabs will be possible on all aspects in near treeline and below treeline terrain as more new snow impacts our area.  Another foot or more of snow is possible above 7000' today.  How this new snow bonds to the old snow surface and/or weaknesses within this new storm snow will be of concern today.   

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    3

    As our recent storm snow continues to settle and gain strength, deep slab avalanches are becoming unlikely but not impossible events.  Deep slab avalanches are characterized by failure more than 3 feet deep in the snowpack and could be large wind slabs, storm slabs or have failure deeper down in the snowpack to the Jan. 9 or Dec. 15 rain crusts.  These deep slab avalanches could occur on any aspect and at any elevation.  Areas above 9000' still represent a concern where significant rain did not affect the snowpack and the Dec. 15 facets.  While this avalanche problem is becoming unlikely, any deep slab avalanche would have severe consequences.   

Avalanche Discussion

Observations were received yesterday from Negro Canyon (Donner Summit area).  Continued wind transport was observed with reactive wind slabs in the area.  Large cornices were built out along exposed ridgelines.  No signs of storm slab weakness was observed throughout the upper 4' of recent storm snow.  Snow below the Jan. 9 rain crust is still wet and has not refrozen yet.  Numerous creeks and open water existed below 6800' in this area.  

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