Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
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

Human-triggered avalanches remain possible today due to slabs of wind drifted snow lingering on slopes exposed to wind loading and possible slabs of storm snow or sluffs of loose unconsolidated storm snow in more sheltered terrain. MODERATE avalanche danger exists at all elevations.

Problemi valanghivi

  • Wind Slabs

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

    Slabs of wind drifted snow still exist on slopes loaded by the SW winds. Areas near ridgelines, gullies, and on open slopes in near and above treeline terrain represent some places where wind slabs will exist. In many cases, these soft wind slabs may not have fully bonded to the snow below them. People recreating on wind-loaded slopes could still trigger wind slab avalanches today. These avalanches could involve enough snow to bury or injure a person (size D2). Fragile cornices also exist above many wind-loaded slopes. As the winds shift to the N and NE and increase tonight expect blowing snow to form new wind slabs on previously scoured slopes by tomorrow. 

    Cornices above a slope, pillows of wind drifted snow, ripples on the snow surface, and other wind-created textures can help identify where wind slabs exist. Areas sheltered from the wind should hold better snow conditions and less potential for instability. 

    (3/10/2021) 1 to 2 ft deep wind slab failure triggered by ski kick on this test slope.

  • Storm Slabs

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

    The storm snow remains cold and soft in many areas and very few signs of storm slab problems have been seen. Still some potential may exist for a slab of storm snow breaking on a steep sheltered slope today. Sluffs of unconsolidated storm snow on steep slopes also remain possible today. 

    Look for cracking or any signs of slab characteristics within the new and recent storm snow.  In areas where the storm snow does not have slab characteristics, dry loose sluffing will be expected in steep terrain.  If signs of instability are encountered, step back to below 30-degree terrain with no overhead hazards.  

    (3/10/2021) A small storm slab on a test slope likely from 3/9/21.

Avalanche Discussion

If the strong March sunshine comes out today, it could provide enough warming to make triggering one of the wind slabs or storm slabs mentioned above easier or introduce the potential for wet loose instabilities on sunny slopes. 

* Wind slabs continued to form throughout the day yesterday with the continued strong to gale force SW winds.  Natural wind slab avalanches were reported on Meiss Ridge (Carson Pass). Some skier-triggered wind slab avalanche activity also occurred on test slopes on Silver Peak (North of Olympic Valley) and on Castle Peak (Donner Summit). These all failed on weaknesses within the storm snow. 

* More skier-triggered dry loose avalanches (sluffs) involving the new snow were reported on steep sheltered slopes on Castle Peak, Silver Peak, and Meiss Ridge yesterday.

* One storm slab failure was observed on a test slope in sheltered terrain on Castle Peak. It looked like it had occurred on Tuesday night.  This failed on weakness within the new snow. 

* Brief periods of sunshine yesterday started to affect the snow surfaces on some E-SE-S-SW-W aspects yesterday with some minor snow surface warming and stiffening of the new snow.

* Observations did not note signs of instability on the snow layers near the rain crusts below the new snow. 

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