Bulletin d’avalanche

Eastside Region

Eastern Sierra Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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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 activity is unlikely, it may still be possible to trigger a large and destructive avalanche today. Elevated caution is recommended in steep unsupported terrain and in areas with shallow trigger points. Use terrain choice to mitigate your exposure to persistent slab avalanches.

Problèmes avalancheux

  • Persistent Slabs

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

    Persistent Slabs challenge our patience and managing this problem requires extensive evaluation and deliberate terrain choice. Northerly and easterly aspects are of greatest concern today. Particularly in complex terrain near and above treeline, on steep and unsupported slopes, areas with shallow trigger points, and in areas with generally thinner snowpack. 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.

  • Wind Slabs

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

    Increasing winds today may lead to some wind slab development in exposed areas and leeward catchment zones near and above treeline. While we do not expect slab thickness to be large today, resulting wind slabs may form on near surface facets which could lead to increased sensitivity. Recent drifting, uneven snow surfaces, and stiff hollow feeling surface snow are all clues that indicate nearby wind deposits. Do your own localized assessments and be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.

Avalanche Discussion

On a regional scale, our persistent slab problem has been gradually moving towards unreactive, and areas where a skier or rider could trigger a slide are very specific in nature. However, it remains important to keep in mind that avalanches breaking loose in these lower weak layers have the potential to be very large and destructive. We received reports of a large avalanche failing on basal facets within the last 48 hrs. This event highlights the continued potential of this problem.

Ok, so where is this problem likely to live?

Elevated caution is advised on steep unsupported slopes near and above treeline and in areas with shallow trigger points such as rock-strewn slopes and areas near cliff bands. Complex terrain with multiple start zones and aspects, convex rollovers, and variable snow coverage may also be problematic. Complicating this problem is the fact that initiating a failure within this weak layer has also become more difficult. It may take a large load such as a cornice failure or relatively small avalanche, or it could take a skier or rider finding just the right spot. The preverbal “needle in the haystack”.

While triggering a persistent slab avalanche has become more difficult, a resulting slide is likely to be very large, breaking near the ground, and it may not be survivable. If you choose to venture into more complex areas give yourself wide safety margins and use terrain choice to limit your exposure.

Régions couvertes