Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

You may encounter wet snow avalanche problems on all aspects. A small Wet Loose avalanche, a falling cornice, or a person's weight could trigger a dangerous avalanche that breaks on buried weak layers in the snowpack. To manage this hazard, choose lower-angle slopes, avoid overhead hazards, and maintain wide safety margins. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    Freezing levels have generally remained between 10000' and 12000' in the last 24 hours. Warm overnight temperatures and increasing cloud cover led to a poor refreeze overnight. SW winds may remain steady today, helping to prevent wet avalanche problems on wind exposed slopes at upper elevations.  As temperatures and cloud cover continue to increase, we may see a greenhousing effect which will increase the potential for surface warming on northerly, shaded slopes. Even a small Wet Loose avalanche has the potential to break into buried weak layers in our snowpack, producing a much larger avalanche. 

    As the snow continues to warm, rollerballs or pinwheels can be the first signs of instability. Wet Loose avalanches can entrain heavy snow that is difficult to manage or escape from. The best way to manage Wet Loose avalanches is to be off of slopes before they become wet and unconsolidated.

     

    (2/22/2025)

    Large triggered rollers on an east-facing test slope below treeline just before noon.

    Photo: Eastern Sierra Avalanche Center

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3.5

    Persistent Slab avalanches are more sensitive to a person in the southern half of the forecast area and at lower elevations where the slab is thinner (3 feet or less). At higher elevations, particularly from Mammoth north, the slab is thicker (~4 to 6+ feet), and feedback may be unreliable. A very large avalanche could be the first sign a slope is unstable. A smaller wet loose avalanche, cornice fall, or the weight of a person in a rocky area with shallower snow cover, could be all that is needed to trigger an unsurvivable avalanche.

    Managing persistent slabs is difficult. They may be triggered remotely—from flatter terrain adjacent to steep slopes and from terrain people usually think of as safe. Persistent slabs often propagate widely and in unpredictable ways. Tracks on a slope do not mean that it’s safe. Shooting cracks and collapses are clear warning signs of the problem. However, feedback is often irregular. The best option is to minimize your exposure to steep terrain on the aspects and elevations with sugary facets buried under stiffer slabs. Use extra caution in rocky, complex terrain, near convexities, and on slopes with inconsistent snow depth.

    (2/20/2025)

    Cornices hanging over slopes with the persistent slab structure--as you can tell by the step-down crowns on the slope below.

    Photo: Eastern Sierra Avalanche Center

Avalanche Discussion

Although it feels like spring, it is important to remember we still have buried weak layers in our snowpack that could produce deadly avalanches. It's been over a week since our last reported avalanche on buried persistent weak layers. However, targeted snowpack evaluations continue to show these layers have the potential to propagate widely if triggered. 

There have been multiple fatal accidents in the last few days in the Western US  involving persistent slab avalanches. Even though the likelihood of triggering one of these avalanches in our region has decreased, the size of a potential avalanche has not changed. The consequences of triggering a large persistent slab avalanche remain very high. 

We send our condolences to all of those affected by the recent tragedies. We encourage everyone to remain diligent in their decision making while traveling in the backcountry. 

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