Boletín de aludes

Eastside Region

Eastern Sierra Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 8 months ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Avalanches large enough to bury you may become likely on wind-loaded slopes at higher elevations. Rain at lower elevations means you should wait for temperatures to drop to avoid loose wet avalanches. Dense new snow is loading slopes with buried weak layers, and it’s a good day to account for uncertainty by stepping back to increase your safety margins.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Strong southwest winds will have new snow to drift onto leeward slopes today. More new snow at higher elevations and in the Mammoth area means that new wind slabs that form there will be larger and more sensitive. 

    Watch for blowing snow across ridgelines and downwind of trees. Steep slopes below cornices and in gullies will be problem spots. Natural avalanches and shooting cracks in dense snow beneath your feet are warning signs to step back. Seek sheltered slopes with no exposure to wind-loaded terrain above you. That’s the best way to avoid getting caught in a wind slab avalanche. As you’re considering your options, keep in mind that a smaller wind slab avalanche could be enough to trigger an unsurvivable slide that breaks on weak layers buried deep in the snowpack.

    (12/24/2025) Small wind drifted road cut, triggered remotely from snowcat. Visibility not great for other observations.

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    The snow surface got wet to near 11,000 feet yesterday. Temperatures remained above freezing below about 9,500 feet overnight. Precipitation early this morning is still falling as rain at lower elevations and in the southern end of the forecast area. Below the rain/snow line, wet-loose avalanches will be possible. Rollerballs and tree bombs that accumulate snow as they roll down hill are good indicators of an increasing wet-loose hazard. Wet loose avalanches will often start at a single point - like your ski - and fan out as they move down slope. You could avoid the problem by starting your day at a higher elevation trailhead or by waiting until temperatures drop by midday.

    (12/31/2025)

    Rollerballs and small (D1) wet loose avalanches. North aspect, 10,500 ft. near-treeline. Rock Creek. We watched these happen around 12:30 pm. 

    Photo: Eastern Sierra Avalanche Center

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    2–3

    Our current persistent slab avalanche problem falls in the low-likelihood, high-consequence category. While it’s unlikely that a human will be able to affect the old, rotten snow now buried 2 to 3+ feet down, with new and drifted snow loading the same slopes that have a concerning snowpack structure, today will be a good day to step back.

    This is a complex problem. You might not get feedback like collapses or shooting cracks until, boom: an avalanche. The only real way to limit exposure to this problem is to avoid steep slopes where old snow is buried. Persistent slab avalanches can be triggered remotely from adjacent slopes and from flat terrain below. A smaller wind slab avalanche could be just enough load to trigger deeper weak layers. If triggered, they can propagate across and around terrain features that would otherwise confine new snow instabilities. Factor the possibility of an unsurvivable avalanche into your plans and increase your margin for error. 

    (12/31/2025)

    Greg is highlighting the line where snow from the Christmas storm cycle sits atop weak old snow from November. 10,200 ft. near-treeline, Rock Creek.

    Photo: Eastern Sierra Avalanche Center

Avalanche Discussion

New snow today, favoring Mammoth and the Sierra Crest, will be dense and drifted by strong southwest winds. This system started warm, with rain up to around 11,000 feet yesterday, causing small wet loose avalanches and rollerballs area-wide. Until temperatures fall, we can expect increasing winter avalanche hazards above and wet-snow hazards below the rain/snow line. 

Old, weak snow exists near the base of the snowpack above 9,500 feet on northerly aspects. In the northern half of the forecast area, weak sugary snow is capped by a rain crust up to 11,000 feet that can be identified with a probe. South of Mammoth, the rain crust is harder to find. The elevation line for old faceted snow is also higher in the southern end of the forecast area, around 10,000 feet.

In the last week, persistent slab avalanches have failed near the base of the snowpack. Most of these failed during the Christmas storm cycle, but several failed in the days immediately after.  The last recorded persistent slab avalanche was on 12/28.

We have three avalanche problems to consider, and you can bet the snow surfaces will change quickly. Today is a good day to step back and note how the weather will affect surfaces and buried weak layers.

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