Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Recently buried weak layers still need time to adjust to the new snow. In wind exposed areas, deep and cohesive slabs are likely to be sensitive again today. Manage uncertainty by reducing exposure and setting conservative terrain margins.

Avalanche problems

  • Wind Slabs

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

    Winds decreased overnight and natural wind slab avalanches are less likely today. However, blowing snow was visible near and above treeline throughout the day yesterday, and it is likely that fresh wind slabs will 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. 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.

    Large wind slab avalanche.

  • Persistent Slabs

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

    Persistent weak layers in the upper snowpack were responsible for several human-triggered avalanches over the last week. The most recent storm has added consequence to the problem by increasing the potential size of avalanches breaking on deeper layers, while at the same time increasing uncertainty around their distribution and likelihood of human triggering. 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.

Avalanche Discussion

Widespread natural avalanche activity was observed yesterday (3/29/23) near and above treeline. Multiple large natural wind slab avalanches were reported in the Crowley and Mammoth areas. One very large natural avalanche released on a NW aspect at 11,400' on Bloody Mountain. The crown appears to connect around multiple terrain features. This avalanche may have failed within the old snow.

Uncertainty today centers on how the most recent storm layer will affect the sensitivity and distribution of the persistent slab. To account for this uncertainty the spatial distribution of the persistent slab problem has been expanded today to include above treeline terrain.

As yet another impactful storm clears today, considerate travel choices and strategic parking will be appreciated as crews continue to manage the extraordinary snow load this season. 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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