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
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 10 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

MODERATE avalanche danger exists on slopes steeper than 35 degrees on all aspects due to the possibility of loose wet avalanches in near and below treeline terrain and wind slabs in near and above treeline terrain above 8500 ft. Some human triggered avalanches will be possible today. Evaluate snow and terrain carefully, and identify areas where avalanche problems might exist.

Problemi valanghivi

  • Loose Wet

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

    Warm overnight temperatures and lingering cloud cover should mean that a weak refreeze occurred last night if a refreeze occurred at all. Continued warm temperatures and some rain below 8000 ft. will cause wet snow to form on some slopes again today. This wet snow will allow loose wet snow instabilities like roller balls, pinwheels, and some point releases to become possible again today. These wet snow instabilities should remain relatively small and less widespread than yesterday due to the gale force winds expected today, but some of them could still entrain enough snow to cause problems for backcountry travelers. Near and below treeline sun exposed E-SE-S-SW aspects and slopes below 8000 ft. that receive rain this afternoon represent the best places to find loose wet snow issues today. 

    Avoid slopes that are steeper than 35 degrees or have terrain above that is 35 degrees as warming occurs today.  Active roller balls and pinwheels indicate that the snow is loosing strength, and it's time to change aspects or leave steeper terrain.

  • Wind Slabs

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

    Gale force southwest winds will continue to transport any available snow from the windward aspects to the leeward NW-N-NE-E-SE aspects. Due to the melt-freeze cycle that happened yesterday less snow should remain available for transport and most wind slabs that do form today should remain relatively small and not extend very far away from ridgelines. Some larger more problematic wind slabs could form on leeward near and above treeline slopes above 8500 ft. where colder more easily transported snow still exists on some of the windward aspects. 

    Identify and avoid steep wind loaded slopes.  Look for areas of blowing snow, cornice formation, wind scouring, and wind pillows to help determine where wind slabs exist.

Avalanche Discussion

Observations from Andesite Peak on Donner Summit and Tamarack Peak in the Mt. Rose backcountry showed a wet snow surface on all aspects up to the summit of Andesite at 8200 ft. and up to 9200 ft. on Tamarack Peak. The E-SE-S aspects up to 9800 ft. on Tamarack Peak held wet surface snow as well. Widespread loose wet roller balls and pinwheels occurred in both of these areas wherever wet surface snow existed. Tests including cornice drops, ski cuts, and snowpit tests on wind loaded test slopes in both areas did not reveal any cracking or other signs of lingering wind slab instabilities. 

Regioni coperte