Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

A winter storm bringing new snow and high winds means you could trigger avalanches large enough to bury you by this afternoon. Natural avalanches and shooting cracks under your feet are red flags. As the danger rises, stepping back from steep terrain and wind-loaded slopes is the best way to manage the hazard.  

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Drifts will grow in size and sensitivity throughout the day as extreme southwest winds have more and more snow to redistribute onto leeward terrain. They’ll also be larger and more sensitive as you gain elevation. The leeward sides of ridgelines, gully features, and cross-loaded depressions will hold the largest slabs. Openings below treeline could develop sensitive drifts as well. Blowing snow, growing cornices, and natural avalanches will point to the most dangerous slopes. Shooting cracks in stiff, textured surface snow means you’ve found unstable wind slabs.

    Poor visibility could make it hard to see what’s above you. You could stick to lower-angled slopes and simple terrain to limit your exposure.

    (12/12/2024) Photo: Eastern Sierra Avalanche Center

  • Storm Slabs

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

    Snowfall rates will intensify throughout the day. Dense new snow will accumulate on top of cold, soft snow from the last storm, on slippery crusts, or on weak, sugary facets. Where new snow falls on these surfaces—as opposed to the brush and rocks found at lower elevations north and south of Mammoth—slab avalanches will become increasingly likely. Sluffs of loose snow could run in very steep, wind-protected terrain and down to aprons below.

    Steep slopes and convex rollovers will be the likely spots to trigger an avalanche in sheltered terrain. Gullies, cliff bands, and shallowly buried obstacles will increase the consequences of getting knocked down by even small avalanches.

    (12/12/2024) Photo: Eastern Sierra Avalanche Center

Avalanche Discussion

A wet and windy storm will cause a rapid rise in avalanche danger. In Mammoth and north, we could see over an inch of new water by the end of the day. Further south, the most intense snowfall will be near the Crest - around 0.8 inches of new water, with heavy, wet snow down low. Dense new snow will fall on colder, softer snow left over from Thursday’s storm. Under that recent blanket the snowpack varies across the region, and with aspect and elevation.

On shady slopes, a soft, faceted snowpack exists. Exposed northerlies had wind-board or were covered with a facet/crust combo. Solar aspects and lower elevations had melt-freeze crusts over more facets in Mammoth. Below treeline terrain south of Mammoth had much less snow or was bare ground. Snow coverage was most consistent in the Mammoth area and just under the Sierra Crest. You can expect avalanches to be larger and more sensitive in those areas. 

Limited wind data outside of Mammoth is a source of uncertainty in today’s forecast. Manage uncertainty by choosing simple terrain with limited exposure to overhead hazards.

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