Boletín de aludes

Central Sierra Nevada

Sierra Avalanche Center
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Peligro de aludes

Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 10 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

MODERATE avalanche danger exists at all elevations due to newly formed wind slabs and unlikely but not impossible lingering deep slabs. Human triggered avalanches may remain possible today especially in regards to the wind slabs that formed yesterday. Evaluate the snowpack and terrain carefully before committing to any route and use this information to identify and avoid areas of concern. This data can also help find safer areas to recreate where good snow conditions exist.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1

    Strong east winds yesterday and light snow on windward aspects allowed wind slabs up to 2 ft. in depth to form near exposed ridgelines on the wind loaded NW-W-SW aspects and on cross-loaded N and S-SE aspects. Continued wind slab formation should remain limited today since the wind speeds have decreased, but human-triggered wind slab avalanches involving these new wind slabs could still remain possible today.

    Use clues like new cornices, wind-drifted snow, blowing snow and ripples on the snow surface to identify where wind slabs may exist and avoid them. Large cornices still exist along many ridgelines even in areas where the east winds have scoured the slopes below them.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    3

    As the snowpack continues to consolidate, refreeze, and gain strength, deep slab avalanches become more and more unlikely. Deep wind slabs that formed during the storm that may linger in complex or extreme terrain on traditional wind-loaded aspects or deep slabs with a weak layer near the Dec. 15 rain crust may remain in higher elevation areas where little to no rain fell. While triggering one of these avalanches would be very difficult at this point, very large triggers like multiple people on a slope or huge cornice failures in isolated areas may still represent an unlikely but not impossible concern for today.

Avalanche Discussion

Yesterday observations from Donner Peak and Mt. Judah near Donner Pass and the Frog Lake area near Carson Pass showed east winds forming wind slabs on exposed westerly aspects near ridgelines. Ski cuts and kicks on these newly wind loaded slopes produced shooting cracks up to 40 ft. and one wind slab avalanche on a test slope on Donner Peak. Most of these wind slabs measured 6 to 18 inches in depth with one topping out closer to 2 ft and did not extend very far downslope. In Indian Valley between Blue Lakes and Highway 4 and on Carson Pass freezing fog had created a very thin crust on the snow surface.  Snowmobile cuts on numerous test slopes in the Indian Valley area did not produce signs of instability. Snowpit data in that area showed good bonding at the Jan. 9th rain crust and no signs of instability. Signs of settlement and consolidation including settlement cracks around trees existed in all locations. Observations also revealed large, deep holes in the snowpack that extended to creeks or wet ground. Depending on visibility and terrain these holes could prove difficult to see.  

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