Lawinenlagebericht

Eastside Region

Eastern Sierra Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Following heavy snowfall yesterday, strong alpine winds and blowing snow at mid and upper elevations have built large slabs in leeward avalanche start zones. Identify and avoid steep wind-drifted terrain, especially slopes where winds are actively piling on more snow.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2.5

    Southwest winds will continue to build slabs in leeward terrain today and new natural slab avalanches are possible. These slabs may be more than two feet thick. Human-triggered slabs could break on sidewalls or high on the slope, above the party involved, and may propagate across the entire slope causing a large and dangerous avalanche. Be cautious around 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. The best strategy today is to identify and avoid recently loaded leeward avalanche paths and avoid crossing through their start zones, tracks, and runouts.

    Size 2 human-triggered wind slab.

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Storm instabilities have begun to settle, but recent avalanche activity indicates that unstable interfaces existed within the storm snow yesterday. Large avalanches failing within the new snow will be possible in all areas except where strong winds have scoured away the new snow. Step out cautiously in sheltered terrain by testing the storm layers on small test slopes before committing to bigger features. Be cognizant of your exposure to terrain features that increase the consequences of avalanches. This includes road cuts, gully features, cliff bands, and mid-slope depressions. As significant snow accumulates in mountain communities be aware of overhead hazards from roofs and short steep slopes above confined areas.

    Photo: Steve Mace

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    In areas that have held snow since December, persistent weak layers still exist at the base of the snowpack. Over the past month, the snowpack has gained strength, but in areas with a shallower snowpack, the weight of new snow may be enough to overload the weak base.  Hard slabs failing on these layers will involve the full depth and weight of the snowpack. Persistent slab avalanches can propagate long distances, connecting terrain features that typically contain surface instabilities such as storm or wind slabs making for larger and more destructive avalanches that are difficult to avoid. The best way to avoid this hazard today is to stay away from northerly avalanche paths including their runouts below treeline.

    (2/3/2024)

    A very large persistent slab avalanche on Mt. Laurel. This released naturally with the last 48 hours.

    Photo: Everett Phillips

Avalanche Discussion

Recent avalanche activity: Yesterday the Mammoth Mountain Ski Patrol reported widespread avalanche activity during mitigation work. Large slabs failed within the new snow at all elevations. Look for more information on recent avalanche activity as skies clear this morning.

Snowpack discussion: We have been tracking a layer of facets and depth hoar at the base of the snowpack throughout the season. In the northern part of the forecast area, these layers are buried 5 to 7 feet deep under a strong middle and upper snowpack. In the southern half of the forecast area from Convict Creek south to Bishop Creek the layers are closer to the surface and have shown more signs of instability since the last storm. In these areas, snowpack structure and results of stability tests indicate that the layer may be more susceptible to human triggering and loading from new snow and wind. Yesterday's storm underproduced forecasted totals for snow and snow water equivalent, but the new load will have been a good test for basal weak layers in the southern portion of the forecast area.

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