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

As daytime warming occurs, moderate avalanche danger will become possible on E-SE-S-SW-W aspects at all elevations due to loose wet avalanche problems.  With overnight and continuing NE winds through today, wind slabs could exist and develop on SE-S-SW-W-NW aspects near and above treeline.  Evaluate snow and terrain carefully, identify features of concern,

Problemi valanghivi

  • Loose Wet

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

    With less cloud cover and warmer temperatures, loose wet avalanches will become more widespread today.  Most of these instabilities are expected to be in the form of roller balls or pinwheels but some could be larger and entrain most of the recent storm snow that we received.  Loose wet instabilities will be possible on E-SE-S-SW-W aspects and could also occur on NW-N-NE aspects at lower elevations that are receiving daytime warming.

    Avoid slopes steeper than 35 degrees when rapid daytime warming begins.  Once the surface snow becomes wet and deep it's time to change aspects or move off and away from slopes that are 35 degrees or steeper.  Recent human or natural triggered roller balls are an indication that the snow surface is loosing strength and that larger loose wet avalanches may become possible.  Terrain traps can greatly increase the risk of these loose wet avalanches.

  • Wind Slabs

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

    Winds switched direction to the NE around 7pm last night and have been recorded in the 25-35mph range gusting as high as 50mph.  NE winds are forecasted to continue though today in the moderate and up to the strong range.  Wind slabs will be possible on SE-S-SW-W-NW aspects near and above treeline.  These wind slabs are expected to be small and limited to the most wind exposed terrain.

    Identify and avoid steep wind loaded terrain where wind slabs exists.  Look for signs of recent avalanche activity, blowing snow, wind pillows, cornices, and human triggered snow surface cracking.  Avoid slopes steeper than 35 degrees where signs of wind slabs are present.  

Avalanche Discussion

Observations were made and received yesterday from Silver Peak (Pole Creek area), Mt. Judah (Donner Summit area) and Mt. Tallac (Desolation Wilderness area).  Natural wind slab avalanche activity was reported from each area that occurred at some point towards the end of the storm cycle.  Small wind slabs were still reactive in the morning on Silver Peak with ski cuts.  Limited active wind loading was observed on Mt. Tallac with more wind transport seen on Mt. Judah.  Snowpack tests on Silver Peak and Mt Tallac showed these wind slabs gaining strength with propagation being unlikely.  Loose dry avalanches (slough) were skier triggered on Mt. Tallac in steeper below treeline terrain.  Some minor loose wet roller ball activity was noted on Mt Judah and Mt. Tallac with wet snow at all locations below 7000' by mid day.

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