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
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 11 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Pockets of MODERATE avalanche danger linger near and above treeline on all aspects on slopes 35 degrees and steeper due to recently formed wind slabs. Pockets of MODERATE danger are possible above 8,000' in near and below treeline terrain on NW-N-NE aspects on slopes 35 degrees and steeper due to potential developing persistent slabs. For all other areas, avalanche danger is LOW. Thoughtful, deliberate decision making remains paramount for avoiding human triggered avalanches in the backcountry today.

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs that formed within the past 24 to 60 hours will continue to gain strength. Difficult to trigger wind slabs generally 1 to 3 feet thick linger on all aspects in near and above treeline terrain due to shifting winds over the past two nights. These wind slabs are stiff and easily identified along ridgetops as pillows directly below small cornice and wind features. Avoidance or alternate slope entry/exit locations are the best mitigation options when areas of cracking are observed around these wind slabs. Glossary of terms

  • Deep Persistent Slabs

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

    Persistent slabs are a developing concern above 8,000' in near treeline and below treeline terrain on NW-N-NE aspects. In these northeast wind protected areas, near surface facets have been observed at the old/new snow interface. The concern focus on an intensification of stress at the base of the recent new snow. As the recent storm snow settles, bonds, and gains strength, the area of greatest relative weakness within the snowpack will shift down to buried near surface facets at the base of the storm snow. This may actually lead to a decrease in stability over what was observed the past two days. This also means that previous tracks on a slope from the past two days will have no bearing on current slope stability as the snowpack is changing daily. Handpits will easily detect the presence or absence of near surface facets at the base of the storm snow. Snowpit tests will indicate if and when this layer interface is becoming problematic. Glossary of terms

Avalanche Discussion

Observations made yesterday on Silver Peak (Pole Creek area) revealed a slow to settle snowpack on northerly aspects and a rapidly settling snowpack on solar aspects. Significant areas of melt were noted to occur during the day below 7,000'. The recent new snow was decently well bonded to rain crust on northerly aspects. No evidence of buried near surface facets at the old/new snow interface was found below the high point of travel at 8,000'. This matched well with the known distribution of buried near surface facets in other locations around the forecast area. Snowpit tests performed at 8,000' on a N aspect near treeline indicated that minimal weakness remained within the recent storm snow and that it was slowly becoming increasingly cohesive. Wind slabs with minimal skier triggered cracking were observed along ridgetops, only extending a short distance down slope. Glossary of terms

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