Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A person could trigger consequential and unpredictable avalanches today.  Buried weak layers 3-6 feet below the surface on shaded aspects are of greatest concern. Fresh wind slab avalanches remain reactive to the weight of a human and may be enough to trigger a larger and more destructive avalanche. Using conservative terrain choices and maintaining a wide safety margin are the best ways to manage the hazard.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3.5

    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 and at lower elevations where the new slab is thinner (~1 meter). At higher elevations, particularly from Mammoth north, the new slab is thicker (~1.5-2 meters), and feedback may be unreliable.  A very large avalanche could be the first sign a slope is unstable. Keep In mind that a smaller wind slab avalanche, or the weight of a person in a rocky area with shallower snow cover, could be all that is needed to trigger an unsurvivable avalanche.

    Managing persistent slabs is difficult. It requires patience and deliberate terrain choice. Persistent slabs may be triggered remotely—from flatter terrain connected to steep slopes and from terrain people may typically 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. Use extra caution in rocky, complex terrain, near convexities, and on slopes with inconsistent snow depth.

    (2/16/2025)

    Large Persistent Slab avalanche. Half Moon Pass -  Rock creek drainage

  • Wind Slabs

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

    Southwest winds increased significantly yesterday and continued overnight. Field observations indicated productive wind loading and reactive wind slab development near and above treeline across the range yesterday. This is expected to continue today. 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 larger avalanches that may propagate across slopes and run to valley bottoms.

    Photo: Steve Mace

Avalanche Discussion

Large to very large persistent slab avalanches resulting from the loading event on 2/13-2/14 continue to be reported. If you haven’t yet looked through the recent observations, I highly recommend it.

Avalanche conditions vary across our diverse forecast area. Generally speaking, the slab thickness will increase as you move from south to north, and as you move up in elevation and closer to the Sierra crest. This means that signs of instability, such as shooting cracks and large collapses, will be more reliable in areas with a generally thinner snowpack. However, as the slab gets thicker and these signs become less common, a very large avalanche failing deep in the snowpack may be the first sign that a slope is unstable. In either scenario, a resulting avalanche is likely to be large and potentially unsurvivable.

We are entering a scary and challenging time. As direct signs of instability become less common, it is important to remember that the consequences of an avalanche are incredibly high. The key word is patience. We have a long season ahead and it will take time for conditions to become more predictable. In the meantime, conservative terrain choice remains your best tool to ensure a safe and fun day in the backcountry.

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