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

Avalanche danger is MODERATE for all elevations and aspects on slopes 37 degrees and steeper due to a suspected poor overnight snow surface refreeze and subsequent loose wet and wet slab avalanche concerns. Continuous snow cover on SE-S-SW-W aspects sufficient to allow for avalanche activity exists only in isolated areas.

Problemi valanghivi

  • Loose Wet

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

    Due to cloud cover and above freezing air temperatures last night, a poor to nonexistent overnight snow surface refreeze is expected. In areas where breaks in cloud cover allowed for a short window of radiational cooling, any snow surface refreeze that did form is expected to be superficial, thin, and weak. As daytime warming progresses, areas of wet surface snow will become widespread in the vast majority of areas. The lack of snow cover remaining on most SE-S-SW-W aspects will limit instability that forms today on those aspects to the isolated areas of continuous snow cover. Of the slopes with continuous snow cover, E aspects will hold the greatest amount of wet snow with carry over from yesterday that did not refreeze last night. Lesser amounts of wet snow will exist on NW-N-NE aspects. Human triggered loose wet avalanches are possible today on slopes 37 degrees and steeper. Keep in mind that secondary terrain hazards such as cliffs and terrain traps below hold the potential to greatly magnify consequences of an avalanche that would otherwise be too small to bury or injure a person.

  • Persistent Slabs

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

    Wet slab avalanches are an unlikely but not impossible avalanche problem today above 7,000' to 7,500' on NW-N-NE aspects on slopes 37 degrees and steeper. Areas where the snowpack remains transitional with wet snow over old snow unaffected by melt freeze are the most likely locations for a wet slab avalanche to occur. Hand pits will easily identify areas where wet surface snow sits over dry old snow below. Deep ski or boot penetration in these areas is cause for concern. If this becomes the situation, avoid the hazard by changing aspects and/or moving to low angle terrain without steeper terrain above. 

Avalanche Discussion

Observations made yesterday on the north side of Carson Pass revealed a well established spring type snowpack on E aspects. Snowpit data indicated a very strong and supportable rain and melt-freeze crust exists in the top 12 inches of the snowpack with well drained melt forms below. The snowpack was noted as approaching isothermal at the snowpit site (E aspect, 8,900'). Several ski cuts on steep E aspect test slopes between noon and 12:30 pm produced only minor roller balls. No significant evidence of wet snow instability was observed prior to departing this area at 1 pm. Surface snow on NE aspects adjacent to the E aspect mentioned above was more transitional and less supportive. Melt-freeze crust on the NE aspects was more superficial with softer, old snow unaffected by melt-freeze below it. Glossary of terms

Around the forecast area in general, significant melt out has occurred on most SE-S-SW-W aspects. On these aspects large areas of bare ground exist with a few sizable snow patches remaining in isolated locations. In general, continuous snow cover is limited to NW-N-NE-E aspects.

 

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