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

LOW avalanche danger continues through the morning hours today. Following the onset of precipitation, MODERATE avalanche danger will exist at all elevations on slopes 35 degrees and steeper. Avalanche danger will further increasing to CONSIDERABLE danger during the evening and overnight hours at all elevations on slopes 30 degrees and steeper. Expect new wind slabs and storm slabs to form during the afternoon and overnight hours. Natural avalanches are possible tonight.

Problemi valanghivi

  • Wind Slabs

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

    Little to no snow is available for wind transport near and above treeline prior to the onset of new snowfall. This avalanche problem will begin to form this afternoon following to onset of snowfall. The combination of new snow and strong to gale force SW winds will create new wind slabs mainly near and above treeline on NW-N-NE-E-SE aspects. Wind slabs are expected to remain small in size this afternoon, becoming large during the overnight hours.

    Avoid areas of wind slab by avoiding slopes that accumulate blowing snow, new wind pillows, and new cornice formations.  

  • Loose Dry

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

    This avalanche problem will begin to form this afternoon following the onset of snowfall. As new snow accumulates, a slab of storm snow will be deposited on all aspects near treeline and below treeline. In some areas this slab of new snow will be deposited on top of weak near surface facet crystals. In isolated areas, this slab may deposit on top of very weak surface hoar crystals. Anyplace that these new slabs form on top of these weak snow crystals, storm slabs could be very sensitive to human triggering after just a few inches of snowfall. Expected avalanche size will start out small this afternoon, becoming large during the overnight hours.

    Early in the storm cycle, snow surface cracking will be the most likely indication that storm slabs exist in the area of interest. As storm slabs become thicker, signs of instability such as snowpack collapse and whumpfing sounds will become possible. Avoid slopes steeper than 30 degrees in areas where signs of unstable storm slabs are present.

     

  • Loose Wet

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

    Any areas of rain on snow today may create small wet loose avalanches. This is most likely to occur in areas below 7,200' on W-NW-N-NE-E aspects in locations where the snow surface has yet to undergo any melting.  

Avalanche Discussion

Recent observations from around the forecast area indicate that in some locations weak snow crystal types exist at the old snow surface that could lead to instability at the old/new snow interface. The weak crystal types of concern are near surface facets and surface hoar crystals that exist near treeline and below treeline on open slopes that are typically wind protected and shaded. The layers deeper in the snowpack appear in good condition to handle new snow loading.

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