Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Signs of instability have decreased, but the weak base continues to be a concern in areas with a shallower snowpack where weak layers are nearer the surface. Lingering unstable wind slabs may be found at upper elevations. Choose terrain carefully. While avalanches are becoming less likely, the consequences of being caught in one have not decreased.

Avalanche problems

  • Persistent Slabs

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

    You are more likely to trigger a large persistent slab avalanche in areas with a generally shallow snowpack. In areas with a deeper snowpack, shallowly buried rocks, trees, and convex rollovers can act as trigger points. Persistent slab avalanches can be triggered remotely from flat terrain below or adjacent to steeper slopes and may propagate long distances and beyond terrain features that typically contain surface instabilities like storm or wind slabs. If triggered the resulting avalanche may involve the full depth and weight of the snowpack. Traveling on slopes less than 30º without overhead hazard is the most effective strategy for reducing risk.

    Large persistent slab avalanches in Mammoth Rock Bowl and near the Poop Chute that failed naturally overnight on 2/4.

    Photo: Steve Mace

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Unstable wind slabs may be present on all aspects at upper elevations. Low-density, wind-drifted surface snow has settled into a more cohesive slab, while the weak snow between it and the older wind slabs has not gained strength. Be suspect of terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, gully features, and cross-loaded depressions. The consequences of being caught in a small avalanche could be magnified in steep terrain. Keep in mind that even a relatively small avalanche breaking in the upper snowpack has the potential to step down to weak layers at the base of the snowpack and may result in a much larger and more destructive avalanche.

    (2/11/2024)

    Cracking on steep W test slopes NTL. Failure plane is down 20 to 30cm - grains at interface are stellar precip. particles.

Avalanche Discussion

Avalanche activity: A few small wind slab avalanches have been reported in steep terrain near treeline in the past 48 hours.

The past storm has increased access and use of avalanche terrain from Rock Creek to Bishop Creek. Initial reports from these areas describe a shallow snowpack layered over early-season weak layers. Following the last storm widespread signs of instability were reported, such as slope scale collapses and long shooting cracks. While signs of instability have decreased, human-triggered persistent slab avalanches are more likely in these areas. 

The likelihood of triggering an avalanche at the base of the snowpack varies between drainages and, in some cases, across the same slope. Managing persistent slab instability requires extensive snowpack evaluation and deliberate terrain choice. Be careful extrapolating observations from one area to another. Once out in the mountains, signs of instability may or may not be obvious. It may be necessary to probe and dig to check on the presence and depth of buried weak layers. It can be difficult to temper expectations and continue to make conservative choices, particularly when it feels like winter has finally arrived. Safer travel options today include sheltered terrain with deeper uniform snow depth, slope angles under 30°, and without overhead hazards.

 

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