Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

MODERATE avalanche danger exists today due to lingering wind slabs and loose wet avalanche problems that will form as the sun comes out and the day warms up. This afternoon's sunshine and warming may also weaken the lingering wind slabs. Human-triggered avalanches large enough to cause problems for backcountry travelers are possible today. Wet slab avalanches should remain unlikely today, but they are not impossible. Avoid slopes where wet snow or wind slabs exist.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Despite slightly cooler temperatures and breezy weather today, the strong April sunshine and daytime highs above freezing should provide enough warming for loose wet avalanches to become possible again today. The new snow from last night and this morning and the storm snow from Monday night that has not fully transitioned to corn could easily become wet and slushy this afternoon and loose wet avalanches could entrain all of this snow. Human-triggered loose wet avalanche activity will become possible on any slopes that receive sunshine today especially on those slopes where the most new snow exists. Loose wet avalanches should comprise the majority of the wet snow issues today, but some isolated wet slab avalanches are not impossible in sun-exposed areas on any aspects/slopes that hold more than a few inches of new snow.

    Avoid slopes where signs of rapid warming like sticky wet surface snow, roller balls, pinwheels, or other signs of wet snow exist. Once the sun hits the slopes today, the snow may become unstable and less fun to recreate on. Seek out shaded, sheltered slopes where the snow remains cold and non-wind-affected for better and safer recreation.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Fragile wind slabs and cornices may still linger on or above wind-loaded N-NE-E aspects as well as on cross-loaded NW and SE aspects in near and above treeline terrain. Human-triggered wind slab avalanches remain possible today and could involve enough snow to bury or injure a person. The largest and most fragile wind slabs will exist in areas where the most new snow has accumulated. As the sun comes back out this afternoon, rapid warming could also weaken the bonds holding these wind slabs and cornices in place and make them more fragile and easier to trigger.

    Clues like cornices above slopes, drifted snow, ripples in the snow surface, and other wind created textures can help identify where fragile wind slabs may exist. Use this information to avoid the wind slabs and to find sheltered non-wind-affected snow to travel on.

Avalanche Discussion

Yesterday observations from Negro Canyon, Granite Chief, and Ralston Peak all found easy-to-trigger loose wet instabilities on sunny slopes. On Ralston and Granite Chief where more new snow existed, the loose wet instabilities entrained more snow. Avalanche activity that likely occurred on Tuesday afternoon also existed in all three areas in the form of large cornice failures and large loose wet avalanches on Granite Chief, in Negro Canyon, and on Donner Peak. A wind slab avalanche had occurred on Ralston as well. Observations targeting the wind slab issue on Ralston yesterday show ongoing wind transport and wind slab formation as well as lingering instability associated with the wind slabs. 

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