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 12 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Human triggered avalanches remain possible today. Above 8,000 ft, MODERATE avalanche danger exists on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper due to lingering dense wind slabs and storm slabs. Some isolated areas of unstable storm slabs may linger on isolated terrain features on other aspects. Don't let the new snow lead to careless decision making. Specifically choosing slopes based on slope angle will be the difference between "getting lucky" and "getting it done" in the backcountry today.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2

    Human-triggereable wind slabs may still remain on wind loaded and cross loaded NW-N-NE-E-SE aspects. Most of these slabs should exist in near and above treeline terrain but some could have formed in below treeline terrain or in more sheltered areas due to the strong winds during this storm. These dense heavy wind slabs rest on top of old crusts that have a layer of softer snow below them on some northerly aspects. While these slabs may have become more difficult to trigger, human triggered avalanches involving these winds slabs remain possible. These dense and hard wind slabs can break above the person who triggers them or could be triggered by the 2nd, 3rd, 4th, or nth person on the slope. Typical obvious clues of instability and other tests may not provide reliable data as to whether or not these wind slabs will break. Wind loaded slopes steeper than 35 degrees above 8000 ft, represent the most likely places to find unstable wind slabs. Wind loaded slopes 38 degrees and steeper, couliors, unsupported slopes above cliffs, or slopes in complex or extreme terrain could be especially problematic today. Some of these slabs could fail on or just below the old snow surfaces and could propogate along those old snow layers.

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2

    Some unstable storm slabs may linger in wind protected areas above 8,000 ft. While these have become more difficult to trigger today due to consolidation in the new snow, human triggered storm slab avalanches with depths of 6 inches to 1.5 ft, will remain possible on slopes steeper than 35 degrees today in wind protected areas in both near and below treeline terrain. Some of these slabs could fail on or just below the old snow surfaces. Northerly aspects steeper than 38 degrees above 9000 ft. where the soft layer below the old crusts remains will represent the best places to trigger these slabs.

Avalanche Discussion

Yesterday a skier triggered a wind slab avalanche north of Relay Peak in the Mt. Rose backcountry. This slide measured about 80 ft. in width with a 2 ft. crown and broke above the spot where the skier initially triggered the avalanche. It ran down hill for about 300 ft. This slide occurred on a 40 degree, N facing slope at about 9500 ft. On the east ridge of Tamarack Peak some snowpit tests indicated instability, while on Relay Peak snowpit tests did not show signs of instability. On Castle Peak snowpit data and observations showed quickly consolidating new snow. Farther south near Frog Lake off of Carson Pass, snowpit data again showed instability at the base of the new snow. The suspect weak layer in the reported avalanche and the tests on the east ridge of Tamarack and near Frog Lake was the layer of softer snow below the old rain crust. This layer could be starting to act more like a persistent weak layer in some places due to the new slab on top of it. 

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