Bulletin d’avalanche

Eastside Region

Eastern Sierra Avalanche Center
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Danger d’avalanche

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

Points saillants

While natural avalanche activity is not likely today, the weight of a skier may be all it takes to trigger a large and destructive avalanche.  Persistent slab avalanches are our main concern and will be most likely on Northerly and Easterly terrain at all elevations. Human triggered wind slab avalanches will also be possible today near and above treeline.  CONSIDERABLE avalanche danger persists at all elevations. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential.

Problèmes avalancheux

  • Persistent Slabs

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

    Our recent storm snow has begun to consolidate into a supportable and cohesive slab of new snow.  The thickness of this new snow will vary from one end of the range to the other, but the common thread is that a significant load has been added to a minimal and, in many areas a very weak base. The weight of a skier or a small wind slab avalanche might be all that is needed to tip the scales and trigger a large destructive avalanche.

    Persistent Slab problems challenge our patience. Managing this problem requires extensive evaluation and deliberate terrain choice. Don’t be afraid to investigate the lower reaches of the snowpack to get a look at the old snow. Remember that persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities such as wind or storm slab and in some cases persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazard that may reside above you, and use terrain choice to limit your exposure.

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–3

    Winds are expected to drop significantly today with relatively light winds expected at all elevations. Limited redistribution today will make natural wind slab activity unlikely however, significant wind transport was reported near and above treeline yesterday and resulting wind slabs may still be reactive to human triggers. It is important to remember that even a small wind slab avalanche today might be enough to trigger a larger and more destructive Persistent slab avalanche.  Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions. Blowing snow, recent cornice growth, stiff hollow feeling upside-down snow and a textured, uneven snow surface are all signs of recent wind transport. Use these signs to identify and avoid slopes with recent wind deposits. 

Avalanche Discussion

Make no mistake, we are dealing with a dangerous snowpack at the moment. One that we are not used to seeing here in the Sierra. Human triggered avalanches remain LIKELY, and resulting avalanches have the potential to be very large and destructive.  Top of our minds is our Persistent slab problem.  Field observations continue to highlight signs of instability such as recent avalanche activity, slope scale collapsing, shooting cracks and propagating test results. All these signs point to a weak structure and the ability for fractures to propagate across the land scape.  Patience is KEY right now, allowing powder fever to get the best of you could be a costly mistake today. Extensive evaluation and deliberate terrain choice are crucial. When uncertainty is high, keep it simple and avoid avalanche terrain.

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