Bulletin d’avalanche

Eastside Region

Eastern Sierra Avalanche Center
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Danger d’avalanche

Thu
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

Over the past 24 hours, strong and shifting winds built new slabs on a range of aspects near and above treeline. Be careful entering steep bowls and depressions down slope from ridges where it may be possible to trigger a dangerous hard slab avalanche.

Problèmes avalancheux

  • Wind Slabs

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

    Small amounts of new snow last night combined with strong and shifting  winds over the past  24 hours mean that you can find new wind slabs in leeward catchment zones on all aspects today. Hard wind slabs may feel strong under a rider's weight, but can fail suddenly and unexpectedly and accelerate down slope quickly. While we do not expect these fresh deposits to be large in size, they could have elevated consequences in complex or exposed terrain.  Larger more consequential avalanches may be possible to find in isolated areas where older wind deposits are resting on weak underlying snow. Watch for clues like blowing snow, large fresh drifts, and hollow upside-down feeling snow. Be suspect of terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, mid-slope convex rollovers, and cross-loaded depressions.

    (2/13/2023)

    Large natural avalanche caused by drifting snow in sheltered leeward terrain below cliff bands. Likely a natural release on 2/11/23.

Avalanche Discussion

Yesterday, evidence of a Natural Wind Slab in Dream Bowl was reported in the June Lake backcountry on a NE aspect at 10,200'. The avalanche was unwitnessed and likely released naturally within the last 48 hours. It falls into a pattern of similar avalanche activity in recent weeks that includes avalanches on Mt. Tom and in Virigina Lakes.

It is worth reading yesterday's avalanche observation as it is an excellent analysis of the complicated structure of the upper snowpack. Over the past month calmer weather with intermittent light snowfall and strong wind events have created a mix of peristent grains in the top ~40cm of the snowpack sandwiched between layers of wind slab. The most problematic terrain seems to be mid-slope north and northeast start zones near and above treeline. In these isolated areas soft snow was sheltered from sun and wind for long periods before wind events created strong layers over top of the weak snow.

We are in for another cold day today. It will be a good idea to keep the extra layers in your pack and carry emergency shelter equipment. 

Régions couvertes