Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Exercise a heightened level of caution in the backcountry today and consider avoiding avalanche terrain in areas where signs of instability are present such as active drifting, snow surface cracking, snowpack collapsing, audible whumpfing sounds, or recent avalanches. Unstable slabs of wind drifted snow remains an ongoing concern for today. In isolated areas, avalanches failing 2 to 3 feet deep could occur at the bottom of the most recent storm snow layer.

Avalanche problems

  • Wind Slabs

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

    Winds out of the SW have continued to drift low density snow and deposit it near ridgetops and into gully features. Avalanche concerns remain ongoing for areas where this drifted snow has deposited as a cohesive wind slab. Over the past several days, wind slabs have been gradually increasing in density.

    Wind slabs remain most widespread in near treeline and above treeline terrain across NW-N-NE-E-SE aspects. Identify the areas of concern near ridgetops and gully features where wind drifting snow is depositing. Slopes below cornice features are highly suspect. Consider avoiding travel in areas with obvious wind loading, snow surface cracking, or recent avalanches.

    (3/6/2023)

    Continued drifting snow fueling wind slab concerns. Wildflower Ridge, Mt. Judah, Donner Summit, CA

    Photo: SAC

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Shallow surface instabilities such as sluffs of dry loose snow will likely continue, but deeper a more concerning storm slab avalanche problem may exist today. We received multiple reports of snowpack collapses, audible whumpfing noises, and/or unstable snowpit test results yesterday. All reports of this instability came from SE-S-SW aspect terrain. A layer of faceted snow below a melt-freeze crust that formed last Thurs/Friday and was subsequently buried by the new snowfall starting Saturday, March 4 is presenting as problematic. Any avalanches that fail on this layer will likely be around 1.5 to 3 feet deep and might have wide propagation.

    If you trigger snowpack collapse, whumpfing noises, or see unstable snowpit test results, avoid avalanche terrain. Be aware of exposure to steeper connected terrain above or to the side of your location as remote triggering is not out of the question. There is a high degree of uncertainty surrounding this avalanche problem until more data is gathered.

Avalanche Discussion

  • SW winds have remained ongoing with drifting of new snow observed daily in near treeline and above treeline terrain.
  • Reports of snowpack collapse and whumpfing were received yesterday from two separate locations on southerly aspects in the Mount Rose zone.
  • Reports of unstable snowpit test results were received from southerly aspect terrain on Poulson Peak in the Pole Creek area. Concerning failures occurred on a crust/facet layer at the base of the recent storm snow accumulated since March 4.

Regions covered