Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

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

Fresh wind slabs formed overnight, increasing the likelihood of human triggered avalanches and delaying the snowpack's adjustment to recent storms.  Uncertainty remains around layers that have produced avalanche cycles in the past two weeks. Conservative terrain choice continues to be the most effective strategy.

Avalanche problems

  • Wind Slabs

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

    Light snowfall and increasing west-southest winds brought on another round of wind slab development overnight. New slabs will most likely be found around terrain features that encourage drifting, such as the leeward sides of ridgelines, mid-slope rollovers, gully features, and cross-loaded depressions. Shooting cracks and firm hollow-sounding snow are signs that new wind slabs may be unstable in your area.  Recent avalanche activity, cracking within the surface snow, recent cornice growth, and hollow upside-down feeling snow, are all clues that indicate nearby wind deposits.

  • Persistent Slabs

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

    In isolated areas a reactive crust / facet combination exists at the new/old snow interface from 3/19/23. This layer is now buried up to two feet deep under recent snow from the past week's storms. It is likely that this crust / facet layer contributed to the sensitivity and wide propagation of avalanches in the Sherwins on 3/20 . Continued sensitivity of slabs below treeline, combined with collapsing in the upper snowpack, and confirmed persistent slab activity from south of the forecast area contribute to uncertainty surrounding this layer. Be careful of areas where the snow surface went through a melt freeze cycle during the clear weather preceding this week's storms. These areas are most likely found below 9500' and on steep solar slopes. The most consistent warning signs of this problem have been collapsing and remote triggers on steep convex rollovers. However, feedback may not be consistent and these avalanches could fail unexpectedly and in surprising ways. Tracks on a slope may not be a reliable sign of stability. Be careful around wind loaded and sun exposed terrain at mid-elevations, and in steep clearings below treeline, especially those that end in terrain traps.

    Remote Trigger D2 - E aspect, 8000' Split Drainage

Avalanche Discussion

Snowpack discussion:

During a short window of clear weather between 3/16 and 3/18 a crust/facet combination developed at lower elevations (below 9500' ) and on steep solar slopes up to ~ 10500'. In the past week two significant stroms, one on 3/19 and one on 3/21 added up to 1-2 feet of recent snow over that interface.  Typical persitent slab behavior - avalanches triggered from a distance, slope scale collapses, and continued slab release beyond 72 hours following the storm have been associated with the 3/19 layer.

The February Persistent Weak Layer is buried ~2m deep on a regional scale and avalanches on this layer are now unlikely. In isolated pieces of terrain a large natural trigger could still produce an avalanche breaking within old snow layers from the January / February dry spell.

Recent avalanche activity:

20230323 - Remote triggered D2 on an E aspect at 8000' 3/19 in the Split Drainage / Red Lake area (south of the forecast zone).

20230322 - Multiple remote and rider triggered storm slabs failing on the 3/19 interface.

20230321 - N-D3- Deep Slab, E aspect, 11300' on Mt. Wood

Comments:

Our winter full of high-intensity storms continues to have major impacts on communities, infrastructure, and road crews. Considerate travel choices and strategic parking will be appreciated if you decide to venture out today. With good coverage at lower elevations this winter, recent avalanches have been running further, impacting roadways and buildings in the communities of 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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