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 13 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Early this morning, avalanche danger is LOW for all elevations and aspects. As the day progresses, areas of MODERATE danger will form on all aspects at all elevations on slopes 37 degrees and steeper in response to daytime warming. Small human triggered loose wet avalanches will become possible.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    A marginal to decent snow surface refreeze is expected to have occurred last night due to near to above freezing air temperatures and radiational cooling of the upper snowpack slightly limited by thin cloud cover overnight. As daytime warming progresses, the snow surface is expected to transition quickly today from frozen and supportable to melt phase with developing wet snow instability. Human triggered loose wet avalanches will become possible from late morning onward, especially during the afternoon and evening hours. Most areas of instability will exist on E-SE-S-SW-W aspects, spreading to include areas on NW-N-NE aspects later in the day. With many previous melt-freeze cycles and previous rain events having already occurred this winter and spring, free water drainage from the snowpack is well established. This is expected to keep loose wet avalanche activity limited to human triggered avalanches that are relatively small in size.

Avalanche Discussion

Observations made yesterday on Rubicon Peak (West Shore Tahoe area) revealed evidence of a decent snow surface refreeze Thursday night. During the morning hours, a 3 to 5 inch thick surface melt-freeze crust existed in this area on all aspects up to the high point of travel at 9,100'. The thickness of the melt-freeze crust increased with elevation. Unfrozen wet snow existed below this surface crust. By 12:15 pm on E aspects below 8,300', the crust was fully melted and the snowpack was becoming unsupportable for a person on skis. On N-NW aspects at 1 pm, the snow surface had experienced less melting and remained supportable down to the lower limit of connected snow patches in this area at about 7,100' (photos, more info).

Regioni coperte