Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Incremental wind loading on an uncertain snowpack will maintain elevated danger at upper elevations today. Avalanche hazard ramps up tonight with heavy snowfall from the early hours of Sunday through Monday morning. Leave plenty of margin in today's plans with the main goal of being out of the mountains before sunset.

Avalanche problems

  • Persistent Slabs

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

    Persistent weak layers at the base of the snowpack are still adjusting to stress from the most recent storm. While natural avalanche activity has decreased, the chances of human-triggered avalanches remain elevated. Variation in snow depth combined with the strength of the overlying slab means that classic signs of instability such as collapses or shooting cracks may be inconsistent or absent in areas where persistent weak layers exist. If triggered, the resulting avalanche could break with little warning, involving the full depth of the snowpack. Persistent slab avlanches can propagate long distances, connecting terrain features that typically contain surface instabilities such as storm or wind slabs.  It may be possible to trigger an avalanche from flatter terrain below or adjacent to steep avalanche-prone terrain. Choosing travel routes with lower slope angles and no overhead hazard is a good way to limit your exposure to these types of avalanches.

    Photo: Everett Phillips

  • Wind Slabs

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

    Overnight, lingering snow showers and blowing snow continued to build slabs in leeward terrain. Wind slabs are most likely to be found in steep terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, gully features, and cross-loaded depressions. Hollow-sounding drifts, shooting cracks through stiff or textured surface snow, and the snowpack collapsing under your weight are indications that you have found unstable wind slabs. Keep in mind that even a relatively small wind slab avalanche breaking in the upper snowpack may be enough to step down to persistent weak layers near the ground, creating a larger avalanche involving the full depth of the snowpack.

    (1/24/2024)

    A remotely triggered wind slab avalanche.

Avalanche Discussion

Recent Avalanches: On 2/1/24 Heavy snowfall with up to 2" of snow water equivalent, resulted in a few large slab avalanches involving persistent weak layers and wind-drifted slabs. These released naturally on northerly aspects near treeline in the June Lake Backcountry and the Mammoth Lakes Basin.

Snowpack Discussion: On most aspects and at all elevations, a layer of depth hoar and basal facets is buried between 3 and 5 feet below the snow surface under a strong mid-pack slab. Above the basal weak layers the snowpack is gaining strength. No persistent layers have been reported within January's storm snow, or within the most recent storm layers. Depending on aspect and elevation a thin melt-freeze crust may be present 1.5 to 2 feet below the snow surface at the new/old interface from 1/31/24. Variations in snow depth between drainages and across slopes continue to make the likelihood of persistent slab avalanches difficult to assess.

Incoming storm: The next week is set for the most intense storm yet this season. Over the next 48 hours, 40" to 60" of snow is expected in the Eastern Sierra.  The storm will impact the entire forecast area, with snow accumulation down to valley floors. Terrain that was previously inaccessible due to low snow will likely become ridable for the first time this season. At the same time, avalanche start zones in areas that previously had exposed ground will accumulate enough snow to produce avalanches. In these areas, less data is available for assessments.

Heavy snowfall will cause travel impacts in mountain communities and on highways. Park responsibly so as not to block snow removal crews working to restore access for residents and emergency services. Travel in avalanche terrain is not recommended.

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