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
2 · Modéré
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Périmé — ce bulletin a expiré 13 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

MODERATE avalanche danger exists on slopes 35 degrees and steeper on all aspects in near and above treeline terrain due to wind slabs, the formation of loose wet snow, and unlikely but not impossible deep persistent slabs. MODERATE avalanche danger also exists below treeline on slopes 35 degrees and steeper on the SE-S-SW-W aspects due to the formation of loose wet snow. Although they are becoming more difficult to trigger, large, deep, and destructive avalanches could still occur today.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3

    Large wind slabs still exist on the wind loaded NW-N-NE-E-SE aspects in near and above treeline terrain. Observations have shown these wind slabs at 3-6+ ft in depth. Even though these slabs have become more difficult to trigger due to settlement and consolidation in the storm snow, human triggered wind slabs remain possible. The most fragile wind slabs would remain in complex or extreme terrain; however, the right trigger in the right place could still trigger a wind slab on other wind loaded slopes as well. Large destructive avalanches would result from the failure of these wind slabs.

  • Loose Wet

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

    Daytime warming and sunshine on the new snow could cause some wet snow instabilities to form again today. These should remain limited to surface instabilities like roller balls, pin wheels, and wet loose avalanches. Wet slabs should remain unlikely today, but it is not impossible that the sun hitting new snow could cause some slabs to release especially on the wind loaded SE aspects where wind slabs may already exist.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    3

    In areas above 9,500' deep persistent slabs linger near treeline and below treeline on NW-N-NE aspects. Weak layers of well developed facets and depth hoar remain buried deep in the snowpack in these areas. The strong thick layer of new snow above these weak layers has made triggering them difficult and this kind of avalanche activity has become unlikely. However, it is not impossible for the right trigger in the right place to still release one of these slabs. Areas where a shallower snowpack exists or where trigger points like rocks are closer to the surface could allow humans to still trigger these slides. Locations that are both above 9,500' and near treeline or below treeline terrain represent only a small portion of the forecast area, keeping this problem isolated in distribution.

Avalanche Discussion

Yesterday on Jakes Peak, data indicated that the new snow has started to quickly settle and consolidate. Some lighter storm snow layers still remain buried under heavier layers, but snowpit tests, ski cuts on steep test slopes, and other general observations did not reveal any signs of instability associated with these layers in this area. Near the summit of Jakes where some larger wind slabs typically form, several large rocks remained exposed and only small wind slabs existed. Again ski cuts did not cause failures in these smaller wind slabs.

On the E-SE-S aspects up to 9160 ft and on all aspects below 7600 ft. some wet snow instabilities existed. At the upper elevations on the SE-S aspects some small roller ball activity occurred on steep slopes near exposed rocks. At the lower elevations a wet saturated snowpack existed and skier triggered roller balls and pinwheels occurred on all aspects.

Due to some cloud cover, the views into the Desolation Wilderness remained partially obscured, but glimpses of Dicks Peak did reveal what looked like some large avalanche crowns. Another observer also reported seeing a large crown on Jacks Peak. These slides likely occurred during the storm.

Régions couvertes