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 9 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

LOW avalanche danger exists this morning. The avalanche danger will increase to MODERATE as loose wet avalanches become possible due to daytime warming and intense spring sunshine. Evaluate snow and terrain carefully and move to less steep slopes or slopes with colder more frozen snow once the snow becomes wet and unsupportable. Avoid slopes below large cornices and glide cracks. 

Problemi valanghivi

  • Loose Wet

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

    Loose wet avalanche activity will become possible again today on steep slopes where wet snow exists as the day warms up. Clear skies in some areas should have allowed a thin refreeze to occur despite the above freezing overnight temperatures. Warmer daytime temperatures and intense March sunshine will quickly melt through this thin refreeze leaving deep wet snow on slopes early in the day especially on the sun-exposed E-SE-S-SW-W aspects. Loose wet avalanche activity has the potential to be more widespread and larger today than yesterday on these aspects and could occur on some isolated northerly aspects as well. If more cloud cover develops over the region today, it may limit some of the loose wet activity. 

    Once the snow becomes wet and unsupportable, it is time to move to a different aspect where colder snow exists or switch activities to avoid the wet snow. 

    In addition to the wet snow potential, large cornices still exist above many slopes and glide cracks have opened on some steep slopes. Numerous cornice collapses have occurred during the warm weather, and at least one has triggered a loose wet avalanche large enough to bury a person. It is very difficult to predict when these cornice failures will occur or when glide cracks will release as glide avalanches. Due to their size, unpredictability, and serious consequences, it is best to avoid areas below glide cracks and large cornice features during any warm periods.

Avalanche Discussion

Yesterday observations in the Donner Summit area, showed wet snow on all aspects. Deep wet snow already existed on E-SE-S-SW aspects by 10:30 am. While ski cuts on test slopes did not trigger any loose wet instabilities in the Black Wall area, numerous large cornice failures had occurred in this area in the last 24 to 48 hours. Some of these did trigger small loose wet avalanches as they entrained wet snow while sliding downhill. A larger natural cornice failure occurred on the east face of Donner Peak at 11:45 yesterday. About 40 ft. of cornice broke and fell onto the slopes below. As the large cornice pieces slid downhill they entrained wet snow and the resulting large loose wet snow avalanche involved enough snow to bury a person. It ran downslope for about 700 vertical ft. before coming to a stop in a lower angle section of the slope.

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