Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Strong alpine winds will drift new and recent snow onto leeward terrain throughout the morning. Large natural avalanches are possible. Avoid steep, open slopes and the runouts of avalanche paths where growing cornices and blowing snow indicate sensitive wind slab development. Sheltered terrain without wind-loading overhead is a safer alternative.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    South-southwest winds that have drifted snow onto leeward terrain will continue at perfect snow-blowing speeds throughout the morning. Windward slopes that already had snow available for transport got a refresh with up to 10 inches overnight. Watch for blowing snow and cornices growing atop leeward slopes through midday. Hollow-sounding drifts, shooting cracks through stiff or textured surface snow, and the snowpack collapsing under your weight are warnings that you have found unstable wind slabs. Avoid steep start zones and the sidewalls of couloirs and gullies that are actively being loaded. Sheltered terrain will likely hold softer snow and a safer alternative. 

    (2/20/2024)

    Reactive wind slabs produced slabbing and shooting cracks on leeward test slopes near treeline that face northeast.

    Photo: Clancy Nelson

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–3

    In areas that have held snow since December, persistent weak layers still exist at the base of the snowpack. A crust/facet combo buried 1 to 2 feet below the surface has recently shown signs of instability on isolated slopes. Over the past month, the snowpack has gained strength, but in areas with a shallower snowpack, the weight of recently drifted snow or a wind slab avalanche may be enough to overload these weak layers. Persistent slab avalanches can propagate beyond terrain features and connect multiple start zones, making for larger and more destructive avalanches that are difficult to avoid. Areas with deeper snow cover and the variability across terrain with shallow snow cover have made the problem more isolated, stubborn to trigger, and have also increased uncertainty. The safest way to limit your exposure is to stick to terrain with low slope angles and few overhead hazards. 

    (2/20/2024)

    Shooting cracks that broke through a soft slab down to facets above a thin wind crust.

    Photo: Clancy Nelson

Avalanche Discussion

Small to large natural and explosive-triggered wind slab and loose dry avalanches released over the past 48 hours. The biggest avalanches ran during the storm on 2/19 or during mitigation work at ski resorts. Forecasters in Bishop Creek found reactive soft wind slabs and touchy cornices yesterday.

Up to 0.8 inches of new water and 10 inches of new low-density snow fell across the forecast area overnight. Ridgetop winds have been strong out of the south-southwest and are expected to continue at perfect snow-drifting speeds through the early afternoon today. That continues the trend of the wind-loading observers reported in exposed terrain over the past 24 hours. In very steep sheltered areas, loose dry sluffs could be a problem in confined terrain above cliffs, tree wells, or road cuts.

Under the recently drifted storm snow, the snowpack varies across the region. In the central parts of the forecast area, between Mammoth and June, the mid-snowpack is generally deep and strong. The northern and southern reaches of the forecast area have shallower, more diverse snowpacks. A layer of facets and depth hoar near the ground has been showing improvements, especially in the areas with deep snow cover. This layer is still closer to the surface from Convict Creek to Bishop where snowpack tests have demonstrated that it can still propagate a failure on isolated slopes.

Another notable snowpack layer exists mid-pack across the region. As you were on your Valentine’s Day date, light snowfall buried several crusts. That snow has since faceted and become weak. Forecasters in Bishop experienced isolated collapses and got snowpit test results on that interface yesterday. It has been found in some snowpits in other drainages as well, though with no notable feedback. You can identify it on sunny slopes as a melt-freeze crust, and below the northerly sides of ridgelines as a wind crust. Look for weak sugary snow above and below it and factor the small possibility of triggering an avalanche on that layer into your terrain choices. 

Regions covered