Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 10 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Areas of CONSIDERABLE avalanche danger are expected today near treeline and above treeline on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper due to ongoing wind slab problems. For all other areas, MODERATE avalanche danger exists on slopes 35 degrees and steeper due to potential storm slabs. Loose wet avalanche problems may or may not develop this afternoon on E-SE-S-SW-W aspects depending on cloud cover. Natural and human triggered avalanches remain possible to likely today.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    3

    Wind slab avalanches occurred yesterday. Continued gale force SW to W winds are scouring all snow available for transport and creating wind loading and ongoing wind slab formation in lee areas. The vast majority of wind slabs are expected near treeline and above treeline on NW-N-NE-E-SE aspects. Due to the strength of the winds, some wind slabs may exist in below treeline areas as well. A few isolated slabs may form on the generally windward S-SW-W aspects as winds wrap around localized terrain features.

    Identify and avoid steep wind loaded terrain. Use clues such as recent avalanche activity, test slope failures, blowing snow, cornice formations, wind pillows, and shooting cracks to determine where wind slabs exist. Avoid slopes 35 degrees and steeper that hold wind slabs.

  • Loose Dry

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

    New snow that fell yesterday and last night in wind protected areas below treeline may contain weak layers within the storm snow. In the case that any unstable weak layers did form, storm slabs will be a problem on slopes steeper than 35 degrees. Use clues such as recent avalanche activity, test slope failures, and shooting cracks to determine if storm slabs are present. Avoid slopes steeper than 35 degrees when signs of instability exist.

  • Loose Wet

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

    Depending on the amount of cloud cover clearing that occurs during the mid day and afternoon hours, loose wet avalanches may or may not become a problem today. If skies clear and air temperatures warm, significant roller ball and pinwheel activity is expected. This will be a precursor to loose wet avalanche activity that could be either natural or human triggered. The vast majority of wet snow instability is expected on E-SE-S-SW-W aspects. Wet snow instablility could occur on NW-N-NE aspects as well in sun exposed and/or lower elevation areas.

Avalanche Discussion

Observations made and received yesterday from the Donner Summit, Mount Rose, Pole Creek, and Carson Pass areas revealed a wide range of instability. In the Donner Summit and Carson Pass areas, signs of instability were widespread with natural and human triggered wind slab avalanches occurring. Skier triggered shooting cracks and snowpack collapse were noted in both wind loaded and wind protected areas. Snowpit tests yielded very unstable results. At the other end of the spectrum in the Pole Creek and Mount Rose areas, signs of instability were limited to the presence of significant amounts of new snow and wind loading. Visibility was poor, but no avalanche activity was seen in these areas and snowpit tests did not produce problematic signs of instability. See below for video, photos, and more info.

Regioni coperte