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 12 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Avalanche danger is MODERATE on all aspects at all elevations on slopes 35 degrees and steeper due to the presence of established wind slabs and the possibility of loose wet and storm slab avalanches.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2

    Recently formed unstable wind slabs that contributed to natural and human triggered avalanche activity yesterday remain a concern today. Recent wind loading and ongoing wind transport has allowed for wind slabs up to several feet thick to form near treeline and above treeline on NW-N-NE-E-SE aspects. Human triggered avalanches remain possible today in recently wind loaded areas. In the more heavily wind loaded areas, avalanche size will easily be large enough to bury or injure a person.

  • Loose Wet

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

    As cloud cover decreases today and sun breaks occur, natural and human triggered loose wet avalanches will become possible in sun exposed areas on E-SE-S-SW-W aspects. Roller balls initiating from snow falling off of rocks and trees or from human activity could progress to a loose wet avalanche. Involvement of terrain features such as cliffs and terrain traps could greatly increase the consequences of becoming caught in a small loose wet avalanche.

  • Loose Dry

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

    Storm slabs may exist below treeline on all aspects in areas that held snowcover prior to the current storm cycle. High intensity snowfall yesterday afternoon into last night may have allowed for weak layers to form within the storm snow. Human triggered cracking in wind protected areas below treeline today is an indication of unstable storm slabs in the immediate area. 

Avalanche Discussion

Observations made yesterday on Tamarack Peak (Mount Rose Backcountry), on Andesite Ridge (Donner Summit area), and along the Frog Lake Cliffs (Carson Pass area) showed that snowpack instability was greatest along the Sierra Crest. On Andesite Ridge and along Frog Lake Cliffs, skier triggered cracking and small wind slab avalanches were observed on N-NE-E aspects near and above treeline during the mid day and early afternoon hours. A report was received of a small natural wind slab avalanche that occurred yesterday evening on Wildflower Ridge on the north side of Mt. Judah (Donner Summit area). The avalanche occurred on an ENE aspect around 7,700' in near treeline terrain that traditionally receives very heavy wind loading.

Régions couvertes