Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

An increase to HIGH avalanche danger is expected today in near treeline and above treeline areas due to new snow and wind drifted snow creating wind slabs and the potential for large avalanches. CONSIDERABLE avalanche danger is expected below treeline due to high intensity snowfall creating storm slabs. Travel in near treeline and above treeline avalanche terrain is not recommended. Travel in below treeline avalanche terrain will become increasingly dangerous as the day progresses. Lighting strikes are possible this afternoon.

Avalanche problems

  • Wind Slabs

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

    New snow and wind today is forming new wind slabs on top of the older wind slabs formed by wind drifted snow on the ground over the past two days. This avalanche problem exists mainly near treeline and above treeline on NW-N-NE-E-SE aspects. Some avalanches could be large and destructive up to a size D3, especially if breaking into the older deeper wind slabs. Isolated wind slabs may form below treeline in wind exposed areas along ridgelines and spines due to the strength of the winds.

    Travel in near treeline to above treeline avalanche terrain is not recommended.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    As this storm progresses, a storm slab avalanche problem is expected to become increasingly likely in wind protected areas below treeline on all aspects. Periods of high intensity snowfall may create storm slab instability. There is uncertainty about the burial of surface hoar that may have persisted yesterday in wind protected areas below treeline. In any place where this occurred, increased sensitivity to triggering of storm slabs is expected today.

    Any signs of natural avalanche activity or snow surface cracking in wind protected areas below treeline indicate the presence of unstable storm slabs in the immediate area. If this is the case, seek low angle terrain without steeper terrain above. Keep in mind that poor visibility may make finding safe areas difficult without excellent terrain familiarity or proper use of navigation tools.

Avalanche Discussion

Several wind slab avalanches both natural and human triggered were reported on Thursday from drifting snow under sunny skies. These avalanches occurred above 8,000' on N-NE-E aspects in near treeline and above treeline terrain. Increasing winds yesterday along the Sierra Crest and in the Luther Pass area were noted to create additional areas of drifting snow, likely increasing the size of existing wind slabs.

Below 8,000' the existing snowpack is in good condition to handle rain on snow. Above 8,000' the bottom and middle portions of the snowpack are strong. Snowpack failure is expected to occur either within the upper portion of the existing snowpack (old wind slabs) or within the new snow (new wind slabs or storm slabs).

Regions covered