Bollettino valanghe

Eastside Region

Eastern Sierra Avalanche Center
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Pericolo valanghe

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

Strong ridgetop winds, plenty of unconsolidated snow, and continuing snow showers mean there is a good chance of avalanche activity today, especially in the alpine. Diligently assess the snow and weather as you move up through the terrain. Avoid overhead hazards, like slopes that may be actively wind-loading.

Problemi valanghivi

  • Wind Slabs

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

    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 near ridgelines.  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 wind slab avalanches will be less likely today, but human-triggered avalanches remain a significant concern near and above treeline. Wind speeds should decrease today and shift to the northwest making the pattern of loading less obvious. Be on the lookout for specific slopes that promote wind loading, such as slopes that have large snowfields upwind and start zones that collect and funnel airflow as it crosses the mountains.

    Large skier-triggered wind slab in the June Mountain Backcountry.  Photo: Steve Mace

  • Storm Slabs

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

    In the past 24 hours storm slabs were sensitive to human and natural triggers at all elevations. Large avalanches failing within the most recent snow will be possible in sheltered areas. The size of these avalanches will be more concerning in the Mammoth Lakes area and near the Sierra Crest where snowfall was greatest. Storm slabs tend to gain strength quickly once snowfall tapers off, but are still a concern given how easily they were triggered in some areas yesterday. It will be important to look for signs of instability and to test smaller slopes before committing to more consequential terrain. Carefully assess for shooting cracks in upside-down new snow. Be extra cautious of your exposure to terrain features that increase the consequences of avalanches. This includes road cuts, gully features, cliff bands, and mid-slope depressions. Avoiding steep terrain with overhead exposure to avalanche start zones is the safest way to manage your risk of getting caught.

    (3/30/2024) Storm Slab flank looking downhill.

  • Loose Dry

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

    Multiple loose dry avalanches occurred yesterday and in some cases acted as a trigger for larger slab avalanches in the terrain below. On wind-protected slopes, dry loose avalanches may be a factor again today. The most concerning areas are long, steep features where sluffing snow can build into a larger avalanche. For example, long wind-protected couloirs and extreme terrain well below ridgelines. If transitioning to steep terrain be alert for significant accumulations of new snow that is not bonding well to itself or the old snow surface. 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.

    Photo: Everett Phillips

    Small natural dry loose out of near-treeline terrain in Convict Creek. 3/30/23.

Avalanche Discussion

Recent avalanche activity: In the past 24 hours natural and human-triggered slab avalanches were reported at all elevations and multiple aspects. Above treeline, isolated large natural slab avalanches released just below ridgelines on Mt. Wood, Bloody Mountain, and off of the San Joaquin ridge. Many natural loose dry avalanches occurred in cliffy terrain, especially on north faces. A few loose dry avalanches triggered large storm slabs on the slopes below creating large debris piles on the aprons of alpine bowls near the treeline. Below treeline skier skier-triggered storm slabs up to 18" deep were reported in steep forest openings in the Mammoth Lakes area.

Today avalanche hazards will vary throughout the forecast region depending on local wind patterns and new and recent snowfall amounts. Any of the three problems above may become the primary concern depending on terrain configuration and local weather. Reports of stability from yesterday highlighted this variability with storm slabs ranging from touchy to unreactive on slopes with similar characteristics even within the same drainage. While all reported avalanche activity has been confined to the most recent storm snow it bears mentioning that in isolated, sheltered, north-facing terrain at upper elevations, persistent grains were buried by snowfall overnight on 3/22-23. 

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