Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

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

In sintesi

People could trigger avalanches where slabs of wind-blown have piled up near ridges, in gullies, and on steep open slopes. New snow could also slide downhill on firm surfaces below it in more sheltered terrain. If you see signs of unstable snow, like recent avalanches or cracking in the snow, or if you have any doubt about the slope's stability, you can reduce your risk by using terrain not steep enough to avalanche.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2.5

    Strong and shifting winds have kept piling snow onto a variety of aspects during the last 24 hours and will continue to do so today. Due to the changing wind directions, wind slabs could exist on almost any aspect. In some places, the winds may have stiffened existing wind slabs into hard slabs that can break above a person. Signs of unstable wind slabs included shooting cracks and test slope failures at the base of the storm snow yesterday. Human-triggered wind slab avalanches will remain possible today. They could involve more than enough snow to bury or injure a person, especially if they pull out one of the older wind slabs that exist below them. 

    Clues like blowing snow, cornices above a slope, wind pillows, and snow surface scouring can help identify where wind slabs may exist. However, the shifting winds have created overlapping layers of scouring and loading on some slopes making it harder to identify which slopes hold wind slabs. Assume the wind slab problem could exist on any exposed slope regardless of aspect or snow surface. 

    (4/3/2023)

    Blowing snow on Elephant's Back near Carson Pass. 

    Photo: SAC

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    The new snow accumulated on old firm snow and frozen crusts in many places and did not bond well to those surfaces. Cold weather will slow down the bonding process and allow any weaknesses like graupel layers in the storm snow to linger. The storm snow may still slide off the old snow surfaces or on storm snow weaknesses today. In most places, this would result in shallow sluffs of cold new snow, but a small storm slab avalanche may be possible in areas that received the higher end of storm snow totals.

    Look for cracking in the upper snowpack and signs of poor bonding, like sluffs on steep slopes, as you travel in sheltered areas below and near treeline.  If you see signs of unstable snow, move to lower-angle areas away from steeper avalanche terrain.

Avalanche Discussion

  • Shooting cracks and test slope failures occurred in newly wind-loaded areas near Carson Pass and on the West Shore yesterday. Many human triggered wind slab avalanches have occurred since Wednesday throughout the forecast region. Most of the sunny days in March have seen human-triggered wind slabs, and several close calls have occurred this spring.   Check out our observation page or the Media Gallery below for more information.
  • Large cornices exist along many ridgelines. Some of them have deep cracks behind them. 
  • Unseasonably cold weather, continued NW winds, and increased cloud cover this afternoon should prevent widespread wet snow from forming despite the intense spring sun. 
  • Signs of persistent instability on graupel and crust layers across NW-N-NE aspects within the forecast area have become increasingly isolated and difficult to trigger. Triggering an isolated persistent slab avalanche 1.5 to 4+ feet deep in snowpack has become unlikely on a regional scale but may not be impossible.

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