Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

People could trigger unpredictable avalanches in the northern half of the forecast area from shallow areas or rocky terrain. Red flags from buried weak layers, like cracks and collapses, mean the problem is easier to trigger south of Mammoth. Smaller, fresh wind slabs on leeward slopes, or smaller wet sluffs where the surface thaws, may be enough to trigger an unsurvivable avalanche. Make careful terrain choices and maintain a wide safety margin.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–4

    Prior to the most recent storm, sheltered terrain, steep slopes below treeline, and areas with shallower snow depths had layers of sugary snow throughout the snowpack. The recent storm snow has made slabs thicker and potential avalanches larger. These avalanches are more sensitive to a person in the southern half of the forecast area. From Mammoth, north, feedback may be unreliable and a very large avalanche could be the first sign of instability. A smaller avalanche, or the weight of a person in a rocky area with shallower snow cover, could be all that’s needed to trigger an unsurvivable avalanche.

    Managing persistent slabs is difficult. They may be triggered remotely—from flatter terrain adjacent to steep slopes and from terrain people usually think of as safe. Persistent slabs often propagate widely and in unpredictable ways. Tracks on a slope do not mean that it’s safe. Shooting cracks and collapses are clear warning signs of the problem. However, feedback is often irregular. The best option is to minimize your exposure to steep terrain on the aspects and elevations with sugary facets buried under stiffer slabs. Use extra caution in rocky, complex terrain, near convexities, and on slopes with inconsistent snow depth.

    Persistent slab avalanches that broke in sheltered terrain.

    Photo: Steve Mace

  • Wind Slabs

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

    Winds have shifted to the southwest and increased significantly overnight, drifting snow onto downwind terrain features. Exercise caution near ridgelines, in gullies, and on steep leeward slopes. Wind slabs may appear rounded and textured or sound hollow underfoot. Recent avalanches, shooting cracks, and collapsing in drifted snow are warning signs to dial back your slope angle and stick to wind-sheltered areas.

    Smaller avalanches or falling cornices have the potential to step down into buried weak layers, producing even bigger avalanches that may propagate across slopes and run to valley bottoms.

    Photo: Samantha Rubin

  • Loose Wet

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

    Increasing clouds have caused a greenhouse effect. Temperatures are generally above freezing this morning and the snow surface has had only a surficial re-freeze. Areas of wet surface snow may develop on slopes sheltered from the wind as daytime temperatures rise.

    Rollerballs and pinwheels often foreshadow Wet Loose avalanches. Wet Loose avalanches can entrain heavy snow that is difficult to manage or escape from. Wet Loose avalanches can also trigger larger slab avalanches that break into deeper snow layers. The best way to manage Wet Loose avalanches is to travel when the snow surface is colder and stronger. Time your trips to avoid crossing on or under very steep slopes in the heat of the day.

    (2/15/2025)

    Rollerballs are the most obvious warning sign of wet loose avalanches.

    Photo: Eastern Sierra Avalanche Center

Avalanche Discussion

Avalanche conditions vary across our diverse forecast area. The common thread is layers of weak, sugary facets and facet/crust combos buried under the snow from early February. 

  • If you are traveling near Mammoth or north, areas that got 3 to 5 feet of snow over Valentine’s Day, persistent weak layers are buried deeply. Very large and destructive avalanches broke on old snow during the storm. Though the facets are harder for a person to trigger in most places, rocky or complex terrain with variable snow cover should spook you. You may see no signs of instability before it’s too late. A bigger trigger–like a snow machine, multiple people on the slope, cornice fall, or a smaller wind slab–could set off an unsurvivable avalanche.
  • Winter has finally arrived in the southern portions of the forecast area, and at lower elevations. Shady slopes that had snow–but not enough snow to be worth it–now have a use-able snowpack. Whoops, an unstable snowpack. Direct feedback, like widespread and slopewide collapses, were reported yesterday from Rock Creek, south, and at elevations even below 8,000 feet. 2 to 3 feet of snow fell during the most recent storm, meaning slabs atop the buried facets are large enough to bury you. Low slope angles and low consequence terrain are the best ways to avoid triggering a dangerous avalanche in these areas. 

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