Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snow and wind have made triggering avalanches likely today on slopes where wind-blown snow has piled up. Avalanches may also be possible on slopes in more sheltered areas. Watch out for open slopes and slopes that roll over, and be alert for any signs of unstable snow like recent avalanches, cracks in the snow, or snowpack collapse. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    The combination of strong winds and new snow has created slabs of wind-drifted snow on open NW-N-NE-E-SE aspects in near and above treeline terrain. These wind slabs will likely be sensitive to human-triggering today since they have not had time to bond with the snow below them. In areas where more snow has fallen these wind slabs will be larger, more widespread, and more consequential. In areas where less new snow has accumulated, the winds slabs will be smaller. Wind slab avalanches could involve enough snow to bury or injure a person today.

    Clues like blowing snow, drifted snow, cornices above a slope, and wind-created surface textures can help identify where wind slabs might exist. Recent avalanches or cracking represent sure signs that wind slabs are unstable. Avoiding steep wind-loaded slopes in favor of lower-angle more sheltered terrain can reduce your exposure to avalanche danger and increase your chance of finding more consistent soft snow. 

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Enough snow has fallen in some areas to create slabs of soft storm snow on steep open slopes in near and below treeline terrain. Triggering a storm slab avalanche that fails within the new snow or at the base of the recent snow may be possible today. Failure on old weak snow below the recent snow on some NW-N-NE aspects may also be possible. In areas that have received the most new snow, storm slabs could be large enough to bury or injure a person. In areas where less new snow has accumulated, storm slabs would be less likely to occur and smaller if they do happen. In addition to the possibility of soft storm slabs, loose cold snow could sluff off of steep slopes entraining more loose snow as it slides down the slope. 

    Recent avalanches, cracking in the new snow, snowpack collapse, and whumpfing sounds all indicate unstable snow. Watch out for steep roll-overs and steep open areas where new snow has accumulated. Identify those areas where unstable storm snow may exist before committing to any slope. Less steep slopes will still hold soft, cold snow, and you should be less likely to feel the firm surfaces below the recent snow on them. 

Avalanche Discussion

  • Variable snow surface conditions ranging from firm ice to soft snow still exist under the storm snow. While the storm snow should help smooth out the snow surfaces, it may not be enough to fully insulate backcountry travelers from the old snow surfaces, especially in steeper terrain. 
  • Near-surface faceting during the long dry spell created weak snow in the top portion of the snowpack on some sheltered NW-N-NE aspects. Recent snow has buried this weak layer. It could become more of a problem since it will stay weak while the new snow consolidates and gains strength.
  • Snowmelt has sped up since the beginning of February. Many more obstacles (rocks, bushes, etc) and areas of bare ground have melted out on SE-S-SW aspects.

Regioni coperte