Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
1 · Debole
Limite del bosco
1 · Debole
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

Avalanche danger is LOW for snow covered areas at all elevations on NW-N-NE-E aspects. For all other areas, avalanche danger is generally nonexistent due to a lack of snow cover.

Problemi valanghivi

  • Cornices

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

    Generally stable avalanche conditions exist around the forecast area on a regional scale. The remote possibility of finding that third scenario of the unlikely but not impossible to trigger persistent slab is just enough to warrant continued caution and diligent best practice travel techniques in the backcountry. The faceted Dec 7 persistent weak layer remained reactive for 3+ weeks following the snowfall event that buried and loaded it. It has recently gone quiet in the areas sampled by field observations. Near treeline and below treeline slopes on NW-N-NE aspects that hold continuous snow cover deserve slope by slope evaluation for an isolated persistent slab avalanche problem. Look for stronger, higher density snow on top of lower density snow. If that is the case, stop and evaluate if the weak layer below the slab remains reactive.

Avalanche Discussion

Observations made yesterday on Andesite Peak (Donner Summit area) fell in line with other observations from around the forecast area over the past week. Where areas of continuous snow cover exist near treeline and below treeline on NW-N-NE aspects, generally one of two snowpack scenarios is found. Scenario 1: The faceted Dec 7 layer has gained enough strength that failure has become unlikely under the current level of load. Scenario 2: The slab sitting on top of the Dec 7 facet layer has lost so much cohesion through the near surface faceting process that it will no longer sustain propagation upon collapse. The slab has literally disintegrated. Either way human triggered avalanches have become unlikely. Finding a third scenario of a lingering pocket of isolated persistent slab instability on an isolated terrain feature somewhere within the forecast area is unlikely but not impossible as persistent weak layers and spatial variability are known to present that way.

Regioni coperte