Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Triggering an avalanche is possible today near ridgetops, in gullies, and on open slopes where wind-drifted snow has deposited. Slopes that hold locally deeper, wind-deposited snow have the greatest avalanche hazard today. Move around these areas with caution.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Wind speeds increased last night, with gusts over 100 mph reported from some ridgetop areas. Plenty of snow was available for drifting, making newly formed wind slabs a concern for today. This avalanche problem will exist mainly above treeline and near treeline, but may extend below treeline in isolated areas due to the strength of the winds.

    There are many clues you can use to help identify the most likely locations where wind-drifted snow has deposited into potentially unstable slabs. Clues such as blowing snow, cornices above a slope, ripples in the snow surface, scoured areas on the upwind side of a ridge, and other wind-created surface features all paint a picture of where to find the specific slopes of concern for today's avalanche problem. Recent avalanche activity and cracking in wind-blown snow represent clear signs that the wind slab problem is present.

    Once you identify where wind slabs may exist, you can move carefully around these areas. Choosing wind sheltered terrain can help reduce your exposure to this avalanche problem and lead you to softer, non-wind-affected snow.

    (12/17/2024) A small wind slab avalanche that was triggered by cornice collapse back on Dec 17. This is one example of the type of terrain where wind slab avalanches are possible today. Photo: Public

Avalanche Discussion

Snow levels rising towards 6,500' today aren't expected to produce much in the way of wet snow avalanches. There is more concern for wet snow avalanches tomorrow as rain on new snow occurs closer to 8,000'.

The Dec 12 persistent weak layer and basal facets are still found in the forecast region's southern and eastern portions.  Locations above 8,000-8,500 ft with a shallower and weaker snowpack are the areas of concern. Some snowpit tests continue to produce unstable results in isolated areas, but most data indicates that these weak layers have gained enough strength to support the current snowpack. Our current new snow loading is fairly gradual, making it easier for these old weak layers to adjust to the overlying snow load. That said, if you happen to trigger an isolated snowpack collapse or whumpf sound, it's best to avoid NW-N-NE aspect avalanche terrain in the immediate area.

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