Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 7 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

CONSIDERABLE avalanche danger exists in near and above treeline terrain with MODERATE danger in below treeline areas due to likely wind slab and possible storm slab problems. Human-triggered avalanche activity is likely today.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1

    Strong SW winds and significant amounts of new snow allowed yesterday's nascent wind slabs to grow larger and more widespread during the night. These slabs of wind drifted snow will continue to increase in size and extent as winds continue to transport snow onto leeward slopes today. Human triggered wind slabs are likely and some natural ones may remain possible in areas with ongoing wind-loading. Wind slab avalanches could entrain enough snow to bury or injure a person and could be several feet deep.

    Make a plan that builds conservative safety margins around wind-loaded terrain. Look for signs of wind-loading like cornices above a slope, blowing snow, drifted snow, and other wind created features to maintain awareness of the terrain and conditions. Avoiding these areas in favor of more sheltered terrain and lower angle slopes should help reduce exposure to avalanche hazards and help find more consistent soft snow for recreation. 

  • Loose Dry

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    Changing conditions during the storm left softer lighter snow under more dense snow. This upside-down layering may allow human-triggered storm slab avalanches to be possible today especially on steep open slopes with convex rollovers. Storm slab size should remain limited in most places due to the smaller paths that exist in more sheltered terrain. However, some of them may still involve enough snow to bury or injure a person particularly in areas with terrain traps. 

    Identify where storm slabs may exist by looking for clues like recent avalanche activity, cracking around your equipment, or feeling a density change in the storm snow with quick hand pits or while probing. Moving to less steep terrain will provide a great way to manage the potential storm slabs and still take advantage of the soft snow in sheltered areas. 

Avalanche Discussion

* Yesterday observations from Elephants Hump, Powderhouse Peak, Ward Canyon, Mt. Judah, and Incline Lake Peak all found stormy conditions with strong winds and some new snow accumulations during the day. The Carson Pass and Luther Pass areas had the deepest new snow (up to 6 inches).

* Some shooting cracks and small wind slab failures occurred in response to ski cuts on small test slopes on Powderhouse Peak. 

* In the areas north of Emerald Bay, less new snow had accumulated and signs of wind slab instability were harder to find. 

* In all the areas, a layer of softer snow existed under a layer of more dense snow within the new snow. Not enough new snow existed for a storm slab problem yet but the potential storm snow weakness was there.

As long as skies remain cloudy today warming instabilities should remain unlikely. If the sun does make an appearance, some loose wet snow instabilities could form and warming could exacerbate existing avalanche problems.

Régions couvertes