Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Wed
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Avalanche danger will rapidly increase today following the onset of high intensity snowfall later this morning. Rapid new snow accumulation, drifting snow, and rapid loading of existing weak layers in the snowpack are expected to lead to avalanche activity. Travel in, near, or below avalanche terrain is not recommended today.

Avalanche problems

  • Wind Slabs

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

    Ridgetop winds out of the SW began to increase late yesterday afternoon and are now gale force in speed. Plenty of unconsolidated snow existed on the ground to drift and form new wind slabs last night, especially near treeline. Add to that the expectation that wind slabs will continue to become larger in size today with the drifting of rapidly accumulating new snowfall. The vast majority of wind slabs are expected in above treeline and near treeline terrain across NW-N-NE-E-SE aspects. Wind slabs may form to a lesser degree in below treeline areas due to the strength of the winds. Any wind loaded areas where the slab fails deeper in the snowpack as a persistent slab will allow for deeper, more destructive avalanches with wider propagation.

    Travel in, near, or below avalanche terrain is not recommended today. 

  • Persistent Slabs

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

    Weak layers of graupel have persisted on NW-N-NE aspects both above and below treeline. Signs of instability on these weak layers anywhere from 6 inches to 2 feet below the old snow surface were observed yesterday in the form of snow surface cracking and unstable snowpit test results. Two skier triggered avalanches occurred yesterday in the Ward Canyon area with snowpack failure reported 6 to 8 inches below the snow surface. While the weak layer in these avalanches is unconfirmed, there is a good chance these avalanches were persistent slabs.

    Rapid additional loading of new snow today is expected to add further stress to this weak layer. As more new snow is added to the upper snowpack, potential avalanche size will increase. Persistent slab avalanches are expected to have wide propagation regardless of slab depth. Travel in, near, or below avalanche terrain is not recommended today.

    (3/27/2023)

    Unstable snowpit test results on a graupel layer 2 feet below the snow surface and adjacent to an avalanche that occurred on March 24. The Nipple, South of Carson Pass, CA

    Photo: SAC

  • Storm Slabs

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

    High intensity snowfall today may lead to slabs of unstable storm snow failing at or above the old/new snow interface in wind protected areas. This avalanche problem will become a concern this afternoon with potential avalanche size increasing late day.

Regions covered