Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
1 · Low
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 13 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The avalanche danger is LOW for most areas with consistent snow cover and nonexistent for areas without snow. On a few of the near treeline NW-N-NE aspects that received the most snow yesterday, some pockets of MODERATE avalanche danger may exist where human triggered avalanches may be possible on slopes steeper than 32 degrees. These more fragile areas are mostly likely to exist where small wind slabs formed above persistent weak layers.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    In most areas yesterday's meager amounts of new snow were not enough to change the avalanche conditions. However, a few areas did report 4 to 6 inches of new snow with strong winds. Some of these areas represent the places where signs of instability lasted the longest in regards to the Dec. 7th facet layers. On some near treeline NW-N-NE aspects, the 4 to 6 inches of new snow may have formed small soft slabs or combined with the winds to form a small wind slabs that would allow the possibility of humans breaking the buried persistent weak layer and causing an avalanche. The places that reported the most snow are scattered along the Sierra Crest. Due to the variable winds, variable accumulation amounts, and variation in weak layer strength, diligent observations to determine where wind slabs or soft slabs have formed and what kind of snowpack they formed above will be necessary to determine which pockets of terrain may hold fragile persistent slab avalanche conditions today.

Avalanche Discussion

Yesterday on Andesite Ridge, old weak snow (Dec. 7th facets) still existed in the bottom third of the snowpack on the near and below treeline N-NE aspects. Above this more weak snow resided. The 2 to 3 inches of new snow that had fallen by 3pm had not formed a slab nor did it add enough weight to the snowpack to reactivate those buried weak layers. Above treeline the new snow fell on scoured slopes where numerous rocks and other obstacles still remain uncovered. In this area observations did not reveal any signs of instability yesterday. The only wind slabs noted had formed along the ridge. They were very small (less than 8 inches deep and a few feet wide) and were well anchored by the exposed obstacles.

Regions covered