Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

The storm has cleared, but dangerous avalanche conditions continue today. A large slab of unstable snow now exists over early season weak layers. Large avalanches may release in surprising ways and can be triggered from seemingly safe terrain above, below, or adjacent to avalanche start zones. Patience and careful route finding are the keys to safe backcountry travel today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3

    Wind Slabs are dense layers of snow formed by wind deposition. Multiple large wind slab avalanches released yesterday Near and Above Treeline. Fresh wind slabs continued to build throughout the last 24 hours. Wind slabs are most commonly found on the leeward side of terrain features that block or re-direct winds. Today these areas are most likely just below ridge lines and in sheltered areas Near and Above Treeline that collect wind-drifted snow. Snow plumes along ridgelines and blowing snow along the snow surface are good indications that new wind slabs are building. Hard styrofoam-like snow is a giveaway that winds slabs exist in the terrain around you. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    The persistent weak layer of faceted snow that formed in November has been buried by over 3 feet of snow in the last five days. A relatively small wind slab avalanche or the weight of a skier might be all that is needed to trigger a large destructive avalanche. Persistent slabs will remain a concern even after the new snow has settled. Recent persistent slab avalanches have been reported on Northeast, North and Northwest aspects Above, Near and Below Treeline. Persistent slab avalanches can be remotely triggered from adjacent slopes and flat terrain below a steep slope, and if triggered, can propagate across and around terrain features that would otherwise confine new snow instabilities. Patience is the key to persistent slab risk management. Build wide safety margins into your tour plan and use conservative terrain choices and careful route finding to limit exposure.

Avalanche Discussion

As skies clear and the storm intensity dies down avalanche hazard will remain elevated.  We now have a pattern of persistent slab acitivity in the ESAC zone. With each loading event we learn more about our persistent weak layers. Yesterday I got a good look at a 3 ft. deep avalanche that released on a short steep slope below treeline near Mammoth. This is the kind of "mini-golf" terrain that can be managed by advanced riders when hazard is limited to new snow instabilities, but could be deadly with the deeper problem in the snowpack. Wind slabs are still building in the alpine and the slab is strengthening. This means that wind slabs triggered today will be deeper and propagate longer distances across slopes. Both of these problems might be triggered from, or run into terrain normally considered "safe spots". If you see an avalanche, post an observation, or email us at [email protected].

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