Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

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

Heavy snowfall and strong winds are forecasted for today. Expect very dangerous avalanche conditions to develop. Wind-loaded slopes and the terrain below will be most dangerous. In sheltered terrain, steep convexities and confined chutes above terrain traps will spell trouble. Travel in and under avalanche terrain is not recommended.

Avalanche problems

  • Wind Slabs

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

    Heavy snowfall and strong winds will create dangerous wind slab conditions in exposed terrain. Expect the size and distribution of fresh drifts to grow throughout the day. Avoid terrain features that encourage drifting such as the leeward sides of ridgelines, gullies, and cross-loaded depressions. Avalanches may break across start zones. Reconsider terrain adjacent to steep slopes that you may typically think of as “safe”. Avoid slopes with steep terrain above. Traveling in and below avalanche terrain is not recommended. 

  • Storm Slabs

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

    Heavy snowfall rates of 2 inches per hour are forecasted today. Storm instabilities, both slabs, and sluffs, will be sensitive in steep wind-sheltered terrain. Convexities and confided terrain features deserve particular caution. Even small avalanches can be dangerous above terrain traps like cliffs or creek beds.

    Storm slab avalanche below treeline. (12/30/2022)

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–4

    If the current storm meets expectations, new loading from snow and wind will stress the lower snowpack. A larger trigger such as a wind slab avalanche or large cornice break will be necessary to trigger a deep slab avalanche. While unlikely, an avalanche breaking near the ground has the potential to be very large and destructive. A wind slab avalanche stepped down to weak snow near the ground and destroyed a house in Aspendell on January 9th. Steep and unsupported slopes, large avalanche paths, and areas with shallow trigger points are areas to consider. Uncertainty around deep slab instabilities is high. Deep slab avalanches often fail without warning, they can propagate across and beyond terrain features that would otherwise confine surface instabilities. In some cases, avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin and use terrain choice to limit your exposure.

    (1/12/2023)

    Deep slab avalanche triggered by a wind slab stepping down to weak layers near the ground. This avalanche damaged houses in Aspendell on 1/9

Avalanche Discussion

Snowfall began yesterday around noon. Winds picked up and small wind slabs were sensitive by early afternoon. Periods of moderate snowfall were recorded overnight and winds have increased. Snowfall rates of over 2 inches per hour are forecasted during daylight hours today. If the current storm meets expectations, expect deteriorating stability throughout the day. 

New and wind-blown snow will fall on a variety of recent surfaces. Before precip began to fall, wind-affected snow was common in exposed areas near and above treeline. Warm temperatures and greenhousing on Thursday left crusts at lower elevations. In sheltered terrain above 8000 feet, soft snow from the last storm gradually stiffens as you get deeper into the snowpack. A rain crust lies under the most recent storm snow. 

Persistent weak layers are buried deeply under hard slabs and rain crusts at the bottom of the snowpack. Avalanches failing on old snow are unlikely. However, a large trigger such as a breaking cornice or a wind slab avalanche may be able to initiate a failure in faceted snow near the ground.

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