Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Alpin
1 · Faible
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 13 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Near treeline and below treeline, MODERATE avalanche danger continues on NW-N-NE aspects on slopes 32 degrees and steeper due to lingering persistent slabs.

Human triggered avalanches remain possible. Shallow covered rocks, logs, and stumps are an additional hazard to backcountry travelers. Impact with rocks or trees while caught in an avalanche can greatly increase consequences.

Problèmes avalancheux

  • Deep Persistent Slabs

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

    Just over two weeks have past since the most recent significant snowfall event, and persistent slab instability continues. While some small and very gradual improvement in stability has occurred over that time, it does not negate the fact that human triggered avalanches remain possible. The problematic faceted Dec 7 persistent weak layer remains widespread on NE wind protected slopes near treeline and below treeline on NW-N-NE aspects. Evidence of instability is still encountered on a near daily basis by backcountry travelers. Snowpit data continues to point out the current instability. Avalanche avoidance through travel on sub 32 degree slopes without steeper slopes above remains the best way to mitigate the hazard.

Avalanche Discussion

Observations made yesterday on Andesite Ridge (Donner Summit area) and near Grouse Rocks (Ward Canyon area) matched well with other previous observations from around the forecast area near treeline and below treeline on NW-N-NE aspects. Snowpit data in both locations indicated that the faceted Dec 7 persistent weak layer has become more difficult to collapse, but still shows the ability to propagate. Other recent observations from around the forecast area have also shown some stability improvements and increased difficulty in triggering weak layer collapse. The ongoing propagation potential remains problematic, as it has been observed in snowpit data on slopes with and without ski tracks. This indicates that if the right trigger point is found on the slope, the necessary snowpack ingredients for a human triggered avalanche remain present.

Rocks, logs, and stumps lurk below the snow surface. The ability of the snowpack to keep a person supported above these hazards remains variable and can change greatly over short distances. Travel accordingly to minimize the risk of injury. 

Régions couvertes