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
2 · Moderato
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In sintesi

Over the past 24 hours, large wind slabs were piled onto leeward avalanche start zones by south-southwest winds. There will be fewer "red flags" of instability today compared with yesterday, but slabs will likely remain sensitive to human triggering.  Avoiding large avalanche paths, especially near ridgelines, is your best strategy to avoid being caught in a dangerous avalanche today.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    Yesterday's snowfall tapered off in the early morning and was followed by a significant southwest wind event that lasted until late last night. With abundant soft snow available for wind transport you can expect heavy dense slabs to have formed in leeward avalanche paths.  Because winds decreased overnight the top layer of snow may not be cohesive and may disguise wind slabs immediately below the surface.  Be alert for signs of instability such as shooting cracks and audible slope collapses. Large drifts, recent cornice growth, hollow upside-down feeling snow, and uneven snow surfaces are all clues that indicate nearby wind slabs. 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. While wind slabs may not react to the weight of a rider in all areas, the consequences of a large wind slab avalanche today could be high.

    Wind transport of recent snow on 4/5/24. Photo: Steve Mace

  • Loose Dry

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

    On steep, wind-protected slopes, dry loose avalanches are worth keeping in mind today. The most concerning areas are large terrain features with a consistently steep pitch where cascading unconsolidated snow can build into a larger avalanche. For example, long wind-protected couloirs and extreme terrain away from ridgelines. Be alert for significant accumulations of new snow that is not bonding well to itself or the stronger snow below. In these situations limit exposure to long steep snow slopes overhead, be careful to avoid starting loose snow avalanches above other members of your group, and be aware of terrain traps below you.

    (3/24/2024)

    Multiple loose dry avalanches.

    Photo: Samantha Rubin

Avalanche Discussion

Recent avalanche activity: Yesterday morning during avalanche mitigation work Mammoth Mountain Ski Patrol reported cracking in the new snow and multiple large explosive triggered avalanches. Loose-dry avalanches were reported near the treeline in Convict Creek.

The storm which deposited 23" of snow in the Mammoth Lakes area over the past 48 hours brought much less to other drainages. In Bishop Creek storm totals topped out at 6 inches. The northern part of the zone reported less than one foot. Because of the difference in recent snowfall amounts avalanche danger will likely be less outside of the Mammoth Lakes area and in drainages east of the Sierra Crest. In areas with the most snowfall, there is uncertainty in the stability and sensitivity of large wind slabs formed by yesterday's southwest winds. Decreases in snowfall, temperature, and wind speed over the past 24 hours may lead to slabs being harder to trigger today and fewer signs of instability. However, the potential for a strong over weak structure in the upper snowpack, and the large average size of avalanches near and above the treeline warrants a conservative approach to avalanche terrain.

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