Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

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

Increasing low-density snow and wind are combining to build fresh reactive slabs. Expect the potential size of avalanches to increase over the course of the day. Travel in leeward avalanche paths near and above treeline is not recommended.

Avalanche problems

  • Wind Slabs

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

    Increasing low-density snow, abundant surface snow available for transport, and strong winds are an ideal recipe for wind slab formation.   Expect touchy and reactive wind slabs of varied depths to form on leeward terrain features creating dangerous conditions. In isolated areas along the Sierra crest wind-loading continued yesterday despite the break between storms. In these areas, wind slabs may be thicker and stronger and fail in less predictable ways. The best bet is to avoid wind-loaded leeward avalanche start zones today, especially below ridgelines and around terrain features that block or re-direct winds. If looking for soft snow in sheltered areas at lower elevations, be aware of overhead hazard and avoid the runouts of defined avalanche paths in the terrain above you.

    Wind Slab crown lines in the Sherwins 1/15/23.

  • Storm Slabs

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

    Snowfall began again late last night and up to 9" of snow has fallen as of this morning. As the day begins, expect storm slabs to be small and reactive to human triggers. Another 6" to 12" inches of snow is expected today. As more snow accumulates storm slabs will become larger, more cohesive, and begin to release naturally. By this afternoon they may be large enough to bury a rider. Terrain traps like gullies and tree wells that concentrate debris could increase the consequences of being caught in a storm slab avalanche. As the day progresses, keep tabs on the amount of new snow that has accumulated in the terrain around you.

    Small storm slab that released naturally in dense forest, 1/14/23.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–3.5

    No new evidence of deep persistent slab instability was reported yesterday (1/15) despite heavy snow and wind loading on 1/14. The November layer of faceted snow is now down 1.5 to 2m below the snow surface. At this depth, the deep persistent slab is unlikely to be triggered by a person. However, on 1/9/23 during heavy wind and snow loading a natural avalanche stepped down and released at the base of the snowpack on a NW aspect above Aspendell, Bishop Creek. If triggered, deep slabs can propagate around terrain features that would otherwise confine new snow instabilities creating larger-than-expected avalanches. The possibility, though unlikely, of these larger avalanches is another good reason to avoid wind-loaded start zones of defined avalanche paths.

    Deep debris below McGee near Crowley Lake. 1/11/23

Avalanche Discussion

Although this round of snowfall will be comparatively less than previous storms, fight the urge to become complacent. There is uncertainty as to the sensitivity of storm interfaces from 1/13, 1/14, and wind slab interfaces in isolated alpine areas from yesterday (1/15). Recently, limited access to trailheads, difficult travel, and obscured visibility means that we have less information to make decisions. In cases where in-depth hazard assessment is challenging it is good to step back and look at the red flags, we have at least three today; new snow, wind loading, and recent avalanches. When in doubt err on the conservative side.

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