Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Mon
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Difficult to manage avalanche conditions are anticipated below treeline today on open slopes where a problematic weak layer is receiving rapid loaded. Periods of high intensity snowfall combined with strong SW winds have also created areas of unstable snow near ridgetops. Travel in, near, or below avalanche terrain is not recommended today.

Avalanche problems

  • Wind Slabs

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

    New snow last night combined with gale force SW winds have drifted snow and created areas of new, unstable wind slabs in near and above treeline terrain. Winds slabs will be most widespread on NW-N-NE-E-SE aspects, but could also form to a lesser extent on other aspects and below treeline due to the strength of the winds.

    Additional snowfall and continued blowing and drifting of snow today will continue to fuel this avalanche problem. Travel in, near, or below avalanche terrain is not recommended at this time.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–2.5

    A weak layer of surface hoar was buried under a few inches of snowfall on Jan 29. In some areas, this layer of feathery crystals has remained weak. Rapid loading of 6 to 12 inches of new snow last night followed by another +/- foot of new snow today is expected to overload this weak layer in some areas. Wind protected, open slopes in below treeline terrain across NW-N-NE aspects are the most suspect for holding this weak layer.

    Any avalanches that occur on this weak layer are expected to have wide propagation. Persistent slab avalanches could be triggered from very low on the slope, from connected terrain on the valley floor, or remotely. This type of avalanche could occur in relatively low angle terrain down into the 25 to 30 degree slope angle range.

    (2/4/2023)

    The obvious horizontal line in the snowpack is large, 25 to 30 mm buried surface hoar, Yuba Pass, CA. In other locations, this weak layer is much thinner and sometimes difficult to see in the snowpack.

    Photo: SAC

  • Storm Slabs

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

    High intensity snowfall last night followed by off and on periods of high intensity snowfall today are expected to create areas of unstable snow. This avalanche problem will occur in areas where the new snow is accumulating faster than it can bond to itself or to the old snow surface below. This avalanche problem is expected in wind protected below treeline to near treeline terrain and may exist on any aspect.

    This avalanche problem combined with the prospects for persistent slab avalanches may lead to very difficult to manage avalanche conditions today in below treeline areas.

Regions covered