Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 13 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

This morning the avalanche danger remains LOW for areas with consistent snow cover. As snow and wind impact the region some pockets of MODERATE avalanche danger may form on near and above treeline NW-N-NE-E-SE aspects steeper than 32 degrees. The most likley places where human triggered avalanches could become possible are the near treeline NW-N-NE aspects where the wind slabs could sit on top of persistent weak layers.

Problemi valanghivi

  • Wind Slabs

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

    As new snow and wind impact the region today, wind slabs should start to form on wind-loaded and cross-loaded aspects. Due to the strength of the winds, these winds slabs could work their way into more sheltered areas like tree covered slopes or slopes farther downhill from the ridgelines. In these areas a weak snowpack with buried persistent weak layers already exists and adding even a small wind slab on top of it could be enough to make human triggered avalanches possible. The near treeline NW-N-NE aspects represent the best places where the most serious human triggered avalanches could become possible today. Other aspects and areas where presistent weak layers do not exist will only hold small wind slabs. If the snowfall amounts remain near the low end of the forecasted accumulation, the avalanches issues should remain small and isolated. If snowfall amounts reach the high end of the forecasted accumulation, the avalanche issues would be larger and more widespread. Either way, diligent observations to determine where wind slabs have formed and what kind of snowpack they formed above will help determine where fragile avalanche conditions may exist. Since the forecast calls for most of the snowfall to remain near the Sierra Crest, near the Sierra Crest is also where the most fragile avalanche conditions should form.

Avalanche Discussion

Observations from Lincoln Ridge near Yuba Pass, Anderson Peak, and Scout Peak near Echo Summit all showed a snowpack with the Dec. 7th facet layer buried in the snowpack. On Lincoln Ridge and Anderson Peak a more consolidated layer of snow resided above this persistent weak layer with more soft unconsolidated weak snow at the surface. On Scout Peak the entire snowpack was weak and unconsolidated. In all three areas general observations and snowpit tests did not reveal signs of continued instability. These and other recent observations from around the forecast area indicate that in some areas the Dec. 7th facets have gained enough strength to support the small slabs above them. In other areas the small slab that used to exist above the persistent weak layer has simply lost its slab characteristics and become weak snow sitting on top of weak snow.

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