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
1 · Debole
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Non aggiornato — questo bollettino è scaduto 12 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Pockets of MODERATE avalanche danger linger in recently wind loaded areas near and above treeline on slopes 35 degrees and steeper. In near treeline areas, pockets of recently formed wind slabs exist on all aspects. Above treeline, recently formed wind slabs are focused more on SE-S-SW-W-NW aspects. Below treeline, avalanche danger remains LOW.

The next scheduled update to this advisory will occur January 2, 2015 at 7am.

Problemi valanghivi

  • Wind Slabs

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

    Newly formed wind slabs 6 inches to 2 feet deep exist in a variety of lee areas both near and above treeline. In above treeline areas, wind slab location has proven more predictable with less interruption to wind direction. In near treeline areas, swirling winds created pockets of both deposition and scouring on all aspects. This created pockets of wind slab formation on all aspects near treeline. Human triggered avalanches remain possible, with increased difficulty of triggering expected going into the new year.

    Keep in mind that while increased difficulty of triggering is an indication of increasing stability, it also means that detecting lingering pockets of instability becomes increasingly challenging. Slope by slope stability evaluation and one at a time travel from one well defined island of safety to another are wise choices when managing challenging to detect lingering instability. 

Avalanche Discussion

December 30th observations both made and received from the Mount Rose, Carson Pass, and Donner Summit areas revealed gale force winds, wind transport of snow, and subsequent wind slab formation. Wind slabs were noted in a variety of areas with the most predictable placement above treeline and less predictable placement near treeline due to swirling winds. Skier triggered cracking was noted in areas of wind slab formation. Slab depth ranged from 6 inches to 2 feet. Snowpack failure was noted to occur either within the wind deposited snow or at the old/new snow interface. All failures were noted to occur at or above the uppermost rain crust within the snowpack.

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