Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 11 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

CONSIDERABLE avalanche danger exists in near and above treeline terrain on NW-N-NE-E-SE aspects on slopes steeper than 35 degrees due to newly formed wind slabs. MODERATE avalanche danger exists elsewhere. The largest wind slabs will exist above 8700 ft. where more snow has accumulated. Human triggered wind slab avalanches are likely today, and some small sluffs may be possible. People traveling in the backcountry should make careful snowpack evaluations and use cautious route-finding and conservative decision-making.

Problemi valanghivi

  • Wind Slabs

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

    Above 8700 ft. fragile wind slabs large enough to bury people already exist and could already measure 2 to 4 ft in depth on wind loaded near and above treeline slopes. Wind slabs will become more widespread as more snow accumulates at all elevations today. The upper elevation wind slabs will grow in size and extent, and the smaller wind slabs that existed below 8700 ft. will become large enough to bury people. Human triggered wind slab avalanches are likely today and some natural wind slabs may still be possible. Wind loaded N-NE-E and cross loaded NW and SE aspects on open near and above treeline slopes represent the best places to find fragile wind slabs, but they could also exist in some below treeline areas or in some traditionally sheltered areas due to the strength of the winds. Use clues like blowing snow, cornices above a slope, wind drifted snow, ripples in the snow, and other wind created textures to help identify where wind slabs have formed.  

  • Wet Slabs

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

    Some small loose dry instabilities may occur within the storm snow in non wind affected areas today. These should remain small and limited to point release slides or sluffs. If they do happen, they should not entrain much snow. Sheltered slopes steeper than 35 degrees with cold new snow on the surface represent the best places to trigger these small sluffs. Loose wet instabilities have become unlikely but not impossible since the rain has stopped and the temperatures have dropped, but a deep layer of wet snow will still exist below the surface today. 

Avalanche Discussion

Yesterday 6 to 12 inches of rain soaked snow existed on the snow surface as of 11 am. As the rain continued this layer of wet snow kept getting deeper. Skiers could easily trigger large loose wet snow instabilities like pinwheels and roller balls that grew up to 6-7 ft in diameter as they rolled down the hill and loose wet point release sluffs that entrained all of the wet snow. The rain also cause some cornices to collapse and triggered some natural loose wet instabilities. Ski kicks on one steep test slope did result in some small shooting cracks that traveled up to 18 inches away from their origin.

Regioni coperte