Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

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

Points saillants

There remains a small chance that you could trigger a large slab avalanche today that fails several feet below the snow surface and breaks wider than expected. Smaller, unstable slabs of wind drifted snow may also exist near ridgetops. Plan routes, terrain selection, and safe zones for regrouping around the possibility of an isolated, large avalanche.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    Observations indicate that day to day improvements in the deeper snowpack stability are occurring. No new post storm avalanche occurrences were reported yesterday. No additional reports of snowpack collapses or whumpfs were reported yesterday from newly traveled areas or from areas that were previously unstable. Snowpack tests suggest that the persistent weak layer of surface hoar (weak feathery snow crystals) and facets (weak sugary snow) at the base of 2 to 4 feet of recent storm snow is bonding into the snowpack and gaining strength. While the likelihood of triggering a large to very large persistent slab avalanche that fails several feet deep has decreased, it still remains possible today as the snowpack does not stabilize at the same rate in all locations.

    If you are venturing into terrain where this avalanche problem could linger, choose routes that have options that allow you to divert to non-avalanche terrain if signs of instability such as collapsing or whumpfing are encountered. In between exposing only one person at a time to avalanche terrain, utilize robust safe zones for regrouping that will provide true protection in the event of a large and unexpected avalanche.

    If you desire to minimize your chances of encountering this avalanche problem, travel on S-SW-W aspects or travel only on sub 30 degree angle slopes not connected to steeper terrain above or to the side.

     

    (2/14/2025) Photo: Ming Poon

    The reported persistent slab avalanches that were triggered post storm occurred in below treeline terrain. This avalanche was remotely triggered on 2/14 on a NE aspect. Hidden Peak, West Shore Tahoe area, CA

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Ridgetop winds out of the SW peaked in speed yesterday afternoon and remain strong in speed this morning. Some areas of blowing and drifting snow were reported yesterday. This drifting snow was able to fill in and form some small, shallow wind slabs along the downwind side of ridgetops and along the side of gully features.

    Use clues such cornices, wind drifts, rippled snow surface texture, and active blowing snow to determine the places where unstable wind slabs may exist. Move around these areas with caution.

    (2/14/2025)

    Small wind slab avalanches similar to this one triggered on 2/14 could be triggered today. Andesite Peak, Donner Summit area, CA.

    Photo: Sierra Avalanche Center

Avalanche Discussion

The weak weather system that brought a few inches of snow to all but the far southern end of the forecast area yesterday morning was followed by a period of rapid warming in many areas. Roller balls, pinwheels, and a few size D1 wet loose avalanches occurred as the snow surface warmed on all aspects. Increasing cloud cover and cooler air temperatures are expected to limit wet snow instability today. For tomorrow, sunny skies and warmer air temperatures may bring the return of wet snow instability.

Régions couvertes