Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

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

In sintesi

There is significant uncertainty in the stability of wind-deposited snow at upper elevations. Slabs built in the last 24 hours will be larger as you climb in elevation, and in certain areas may be poorly bonded to the old snow surface.  You can decrease the chances of being caught in a large avalanche today by avoiding steep wind-loaded terrain.

Problemi valanghivi

  • Wind Slabs

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

    Yesterday, wind-drifted snow was reported at all elevations. Snow showers over the past 24 hours added a few inches of new snow with winds continuing at the right speeds to continue slab building.  Large drifts, recent cornice growth, hollow upside-down feeling snow, and uneven snow surfaces are all clues that indicate nearby wind deposits. Do your own localized assessments and carefully evaluate terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, gully features, and cross-loaded depressions. Natural avalanches will be less likely today, but human-triggered avalanches remain a significant concern near and above treeline where larger slabs and more uncertainty in the new/old interface warrant conservative decision making.

Avalanche Discussion

Recent avalanche activity: Mammoth Mountain ski patrol reported stubborn storm slabs up to 8" below the treeline during mitigation work yesterday morning. No natural or human-triggered slab avalanches were reported in the backcountry, but there was limited visibility and all submitted observations focused on below-treeline terrain.

Snow surfaces and new snow: Over the past 48 hours 14" of new snow and southwest winds built cohesive slabs at all elevations. Initial reports from protected low-elevation terrain suggest that the most likely failure plane is a density change where lighter storm snow changes to denser wind-affected snow nearer the snow surface. This density change was stubborn to trigger yesterday. While the new/old interface was not reported as concerning below treeline there is more uncertainty at higher elevations. The sunny spring weather leading up to the current storm led to the development of melt-freeze crusts on most aspects at all elevations. At upper elevations shaded, northerly slopes held onto cold dry snow. In areas protected from the wind, even above treeline, near-surface facet and surface hoar development were reported at the top of a dusting of loose dry snow from 3/16. It will be worth tracking the aspect and elevation of any slab avalanche activity today to see which new/old interfaces are bonding well, and which may hold lingering instability. 

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