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

Human-triggered wind slab avalanches remain possible today. MODERATE avalanche danger exists on wind-loaded NW-N-NE-E-SE aspects 35 degrees and steeper in near and above treeline terrain. Use clues like cornices, drifted snow, ripples in the snow surface, and other wind created textures to help determine where wind slabs may exist. Convex rollovers, areas near rocks, unsupported slopes, couloirs/gullies, and other complex terrain represent the most likely places to trigger wind slabs.

Problemi valanghivi

  • Wind Slabs

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

    Even though last night's additional snowfall remained meager, combined with moderate southwest winds it should have been enough to cause the existing wind slabs on wind-loaded NW-N-NE-E-SE aspects in near and above treeline terrain to remain fragile today. Human-triggered avalanches involving the wind slabs will remain possible today. While any steep wind-loaded slope poses a potential problem, convex rollovers, areas near rocks, unsupported slopes, couloirs/gullies, and other complex terrain represent the most likely places to trigger wind slabs. These wind slabs rest on a layer of softer snow that can serve as a weak layer, and these slabs can break above the person who triggers them. Due to shifting winds during the last few days, wind slabs may have formed in some atypical areas (including some isolated W aspects). Use clues like cornices, drifted snow, ripples in the snow surface, and other wind created textures to help determine where wind slabs may exist. Many of these wind slabs measure 1 to 2 ft. in depth, and avalanches resulting from their failure could involve enough snow to bury a person especially in the most heavily wind-loaded areas or in areas where terrain traps magnify the consequences of the wind slabs.

    Over time these wind slabs will start to bond to the layers below them. Patience, good judgment, cautious terrain selection, and conservative decision making can keep people from triggering more wind slab avalanches today. As a person involved in one of yesterday's avalanches said, "Early season stoke can easily blind decision making. Ski smart & travel smart."

Avalanche Discussion

Yesterday, several skier-triggered wind slab avalanches occurred along the Sierra Crest. On Castle Peak a party triggered one on N facing slope (more info here). Another party triggered one in the Grouse Rocks area on a NE aspect (more info and photos here). Both avalanches occurred on wind-loaded slopes in near treeline terrain with crowns about 1 ft. depth. Both parties triggered the slides at convex rollovers and the resulting avalanches broke above the person who triggered them. In both cases the avalanche caught and carried the person who triggered it but did not bury him. No injuries occurred but both of the triggers said things could have been much worse. Another party reported a small wind slab avalanche on an unusual W aspect on a convex slope in the Donner Summit area. East of the Lake in the Tamarack Peak area, some shooting cracks occurred on wind loaded test slopes and snowpit tests on the test slopes indicated that the layer of softer snow below the wind slabs remained fragile (more info, photos, snowpit).

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