Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Tue
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 still trigger avalanches 2.5 to 6+ feet deep today in sheltered or exposed areas where weak snow lurks below the surface. The largest avalanches remain possible in places where wind blown snow has piled up on top of the buried weak layers. If you see signs of unstable snow, like recent avalanches, cracking, or collapsing, or if you have doubt about a slope, using low-angle terrain not connected to steeper slopes can help reduce the chances of triggering an unexpected avalanche.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    People triggered several persistent slab avalanches and widespread whumpfing/collapsing yesterday. The avalanches all involved enough snow to bury or injure a person; some of them could have buried a car. Some released with people on the slope, people triggered some remotely from nearby terrain, and one failed on a slope with previous tracks when the second person down the slope triggered an avalanche. Check out the avalanche tab for a list.  Most of these have failed on weak layers buried on Jan 2 (buried surface hoar, faceted snow, and/or a crust/facet combo). Some of the larger avalanches may have stepped down to deeper weak layers like facets around the Dec 19 rain crust or even depth hoar near the ground. These weak layers persist longer than typical storm snow weaknesses, and near misses like these remain possible today since people could still trigger large to very large persistent slab avalanches. People can trigger these avalanches from above, below, or to the side of a slope, and they often break wider than expected.

    Persistent slab avalanches could occur anywhere persistent weak layers exist. Observations have found these layers on various aspects and elevations, ranging from sheltered low-elevation areas to the highest, most exposed slopes. Slopes where wind slabs typically form could produce much deeper avalanches.

    Recent avalanches, snow surface cracking, snowpack collapse, or whumpfing sounds indicate unstable, persistent slabs, and signs of wind-loading will indicate terrain capable of producing very large avalanches. The obvious signs of instability may decrease today, but people could still trigger an unexpected avalanche in an area of seemingly stable snow. This scenario may even play out on a slope with tracks on it. If you see any signs of unstable snow or have any doubt about a slope, assume it is unstable. Using low-angle, non-avalanche terrain not connected to steeper areas above or beside can reduce exposure to the persistent slab problem.

    (1/14/2024)

    This very large persistent slab avalanche failed in a wind-loaded area and then triggered another failure lower on the slope. It is from near Highland Lakes around Ebbetts Pass.

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