Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Large human-triggered avalanches are possible today. These are most likely in areas that were wind loaded in the past 48 hours. Increasing temperatures may cause wet snow instability on solar slopes below treeline. Be alert for signs of instability in warming or wind-drifted snow as you change aspect and elevation.

Avalanche problems

  • Persistent Slabs

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

    Cold clear nights in the short windows between our most recent storms have created thin sun crusts and weak layers of near surface facets at various depths within the upper snowpack. These are mostly likely found on slopes that combine sun exposure and wind loading. A stabilizing trend in the weather and settling surface snow may give a false sense of stability. Feedback may be limited and avalanches could be triggered suddenly and fail in surprising ways. Remember that persistent slab avalanches can propagate across and beyond terrain features that would otherwise confine surface instabilities and can be remotely triggered from below or adjacent to steep slopes. You can manage uncertainty by reducing exposure and maintaining good terrain margins.

    Very large natural avalanche. NW, 11,400' Bloody Mountain. 3/29/23.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Multiple human-triggered wind slab avalanches in the past 24 hours indicate that fresh wind slabs may still be sensitive to human triggers today. Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions. Continually assess patterns in the hardness and depth of the surface snow and the layers immediately beneath. Look for shooting cracks and hollow feeling drifted snow as evidence that wind slabs may be unstable in your area. In some areas, weak snow at the new/old interface may make slabs more sensitive and allow for wider propagation and larger avalanches.

    (3/30/2023)

    Natural slab avalanche on Solitude Peak.

  • Loose Wet

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

    An increase in temperatures today combined with light winds and clear skies means that wet snow instability is likely on sunny low elevation slopes. Look out for progressively wetter surface snow on sunny aspects. Rollerballs and pinwheels are the most common signs that the likelihood of wet snow instability is increasing. If these signs are present then it may be a good idea to adjust route selection to avoid passing underneath steep sun baked slopes, especially in confined or cliffy terrain that limits options to escape runouts and could concentrate debris flows.

    (2/11/2023)

    Small wet loose avalanches in steep rocky terrain. More likely below treeline today.

Avalanche Discussion

Recent avalanche activity:

3/30/23: Multiple large skier-triggered wind slabs were reported in the Sherwins and in Bishop Creek, these were all near treeline and included SE through NE aspects.  These slabs most likely released at the new/old interface from the most recent storm.

3/29/23: A very large natural avalanche released mid-storm on a NW aspect at 11,400' on Bloody Mountain. The crown appears to connect around multiple terrain features. This avalanche likely failed within the old snow.

3/29/23: A large natural avalanche released mid-storm on a NE aspect at 8400' above the South Lake Rd. in Bishop Creek. The crown appears to connect around multiple terrain features. This avalanche likely failed within the old snow. Debris ran into the roadway.

The main source of uncertainty today is the sensitivity of wind slabs that formed on 3/29/23. In isolated areas a combination of sun crusts and near surface facets at the new/old interface may mean human-triggered wind slabs are still reactive.

With good coverage at lower elevations this winter, recent avalanches have been running further, impacting roadways and buildings in the communities of Mammoth, Virginia lakes, Mono City, June Lake, and Aspendell. It is important to practice good run-out awareness. Triggering an avalanche above infrastructure could have devastating consequences.  Remember that it often takes multiple passes to clear roadways and trailhead parking. Road crews are working overtime to allow access to communities that have been stranded by heavy snow, avalanche activity, and flood damage. Blocking snow drifts, travel routes, and snow piles makes it impossible for road crews to continue their work.

 

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