Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 8 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

MODERATE avalanche danger still exists in near and above treeline terrain due to lingering wind slabs as well as some potential new wind slabs. While these wind slabs should have become more difficult to trigger, human-triggered avalanches remain possible. 

Problèmes avalancheux

  • Wind Slabs

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

    Shifting winds over the last 48 hours means that wind slabs could exist on almost any aspect in exposed near and above treeline terrain. The largest wind slabs should still exist on wind-loaded N-NE-E aspects and cross-loaded NW and SE aspects but smaller ones may also exist on slopes loaded by last night's NE winds. Some of these wind slabs could involve enough snow to bury or injure a person in the most wind-loaded areas. Most of the wind slabs should be more difficult to trigger today. However, larger triggers like multiple people on a slope or the right trigger in the right spot could still cause them to release especially in complex or extreme terrain like couloirs, cliffy areas, or on unsupported slopes. 

    Use clues like cornices above slopes, blowing snow, ripples, drifted snow, hollow sounding snow, or other wind created surface textures to help identify where wind slabs may exist and avoid those areas in favor of the more sheltered areas where the snow is also more likely to remain softer.   

     

Avalanche Discussion

* Yesterday in complex near treeline terrain below Saucer Lake (Echo Summit / Mt. Ralston area) a snowboarder intentionally triggered an avalanche with a snowboard cut. It ran down the 38 to 40 degree chute, over cliffs, and through a terrain trap (rocky chute). No one was caught in the avalanche but it did involve enough snow to bury or injure a person.

* A natural wind slab avalanche was reported near the ridge of National Geographic Bowl (Granite Chief Wilderness). Stomping on wind-loaded test slopes in this area and on Andesite Peak (Donner Summit) in the afternoon, produced shooting cracks up to 10 ft. long. After few additional kicks on the Andesite test slope, the wind slab slid downhill about a foot. Other wind-loaded test slopes in the Andesite and Castle Peak area did not react to cornice drops, ski cuts, or show signs of instability in snowpit tests. Yesterday morning on Incline Lake Peak (Mt. Rose backcountry), only one of several ski cuts and cornice drops onto test slopes caused a smaller wind slab failure. Blowing snow and active wind-loading was reported along the Sierra Crest and in the Mt. Rose area all day.

* Observations from below treeline terrain on Incline Lake Peak, the Castle Peak, and Andesite Ridge area, and from the Granite Chief area did not reveal active signs of instability, but a loose snow layer (facets) similar to the one found in the Carson Pass and Ebbetts Pass areas that will need to be monitored did exist either below the recent snow or below a crust below the recent snow.

Régions couvertes