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

In sintesi

LOW avalanche danger will persist on all aspects and elevations during the day today. Some unstable snow could still exist on isolated terrain features due to the presence of lingering persistent weak layers. The avalanche danger will increase quickly tonight and rise to CONSIDERABLE as new wind slabs and some small storm slabs form overnight. These avalanche problems mean that careful snowpack evaluation, cautious route-finding and conservative decision-making will be essential tomorrow (and tonight).

Problemi valanghivi

  • Cornices

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

    Avalanche activity will remain unlikely during the day today unless the storm arrives much sooner than expected. The avalanche danger will increase quickly once snowfall begins this evening. During the night new fragile wind slabs will form on leeward aspects and some small storm slabs may accumulate above the potential weak layers (facets) that still exist in the bottom half of the snowpack on some NW-N-NE aspects. Knowing where these layers exist now and how weak they currently are can help make more informed decisions when the snowpack becomes deeper tomorrow. The numerous anchors that protrude through these layers have kept them from becoming continuous over large areas and have kept the pockets of instability small and isolated, but these pockets of instability may become more widespread depending on how much snow accumulates tonight. The anchors also make hitting hard immovable objects while traveling through the snow likely in most areas. 

    For anyone traveling in the backcountry tonight during the hurricane force winds, heavy snowfall, and utter darkness, human triggered avalanches will be likely. For everyone who waits till tomorrow to get out, the snowpack and avalanche conditions will be very different than today making careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Careful and informed trip planning tonight and tomorrow morning can help prevent poor decision making caused by "powder fever" and the excitement of early season snow tomorrow.

Avalanche Discussion

Warmer temperatures and widespread cloud cover caused the snow surface to warm up on all aspects yesterday. Observations from near 10,000 ft. on Red Lake Peak and on Relay Peak both showed moist surface snow and crusts even on northerly aspects. On Red Lake Peak some small wet loose slides occurred on steep south facing slopes and some roller balls occurred on other aspects. Below the surface on Red Lake Peak and Relay Peak, the snowpack consisted of mostly weak layers of faceted snow. Snowpit tests indicated that these layers remain weak but that if they do break, fractures have a hard time traveling along those layers.

These observations match other observations from around the forecast area this week. Many areas have weak layers of faceted snow on the northerly aspects, but tests on these layers only yield obvious unstable results in isolated areas.  

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