Bulletin d’avalanche

Eastside Region

Eastern Sierra Avalanche Center
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Danger d’avalanche

Sun
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
4 · Fort
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Heavy snow and low-elevation rain showers combined with extreme winds have created very dangerous avalanche conditions throughout the forecast area. Natural and human-triggered avalanches are very likely.  Travel on or underneath avalanche terrain is not recommended.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3

    Heavy snowfall and strong to extreme SW winds will create dangerous wind slab conditions on northerly and easterly terrain features, particularly near and above treeline. Expect the size and distribution of fresh sensitive wind slabs to grow substantially today. Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.  Large to very large natural and human triggered avalanches are likely today and avalanches may run long distances and into lower angle, or treed terrain you may typically think of as “safe”. Be cognizant of what is above you today, travel in and below avalanche terrain is not recommended.

    (12/30/2022) Wind slab avalanche -  Lakes Basin, Mammoth Lakes Area

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Snowfall rates increased significantly overnight and heavy snow and low elevations rain are expected to continue throughout the day. Storm instabilities will grow in size and continue to be sensitive as the day progresses. Avoid being on or under terrain over 30° today and be cognizant of your exposure to terrain features that increase the consequences of avalanches. This includes road cuts, gully features, cliff bands, and mid-slope depressions. Be wary of overhead hazards today and avoid being in or underneath avalanche terrain.

    12/30/2022- Storm slab Avalanche - Lakes Basin, Mammoth Lakes Area

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    On a regional scale, our persistent slab problem has become unreactive. However, our current  storm will add significant stress to the lower snowpack. While unlikely, an avalanche breaking near the ground has the potential to be very large and destructive. Steep and unsupported slopes, areas with shallow trigger points, and areas with a generally thinner snowpack are areas to consider. Persistent Slabs challenge our patience and managing this problem requires extensive evaluation and deliberate terrain choice. Persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities such as wind or storm slabs and in some cases persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazards that may reside above you, and use terrain choice to limit your exposure.

    A releitivly small wind slab steped down and triggered a lagre persitant slab avalanche on Willson Butte. 

Avalanche Discussion

The risk of triggering a large and destructive avalanche is high. On the menu today are several diverse concerns with very large consequences.  Sizable dry snow avalanches will be very likely above the rain line. However, it will be a whole different world at lower elevations. Rain on snow almost always produces wet snow avalanches. The rain crust from Tuesday’s storm event will make for a good sliding surface, slab avalanches may initiate and run at lower slope angles than you typically expect, and water may percolate deeper in the snowpack with prolonged rain showers. It won't be out of the question to see wet avalanches breaking near the ground, particularly in areas with relatively thin coverage. Make no mistake conditions in the backcountry are very dangerous and complex today. Some days are just better for making soup.

Régions couvertes