Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Moderate avalanche danger continues throughout the forecast area on slopes steeper than 32 degrees at all elevations due to persistent slabs.  Human triggered avalanches remain possible today.  Evaluate snow and terrain carefully, identify features of concern.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Persistent slabs continue to remain an ongoing avalanche problem around the forecast area.  These persistent slabs may be found on W-NW-N-NE-E aspects below treeline, near treeline, and in some cases above treeline.  Near crust facets that have formed above the Dec. 15 rain crust and below the recent storm snow are the main weak layer in most areas.  Recent avalanches in the last week that have occurred with this persistent slab have frequently been low on the slope in steeper terrain, on convex roll overs, or poorly supported slopes.  Snowpack tests and observations have indicated that this problem is more prevalent along the Sierra Crest than in the Mt. Rose area.

    Persistent slab avalanches are unpredictable and require different terrain management techniques.  These avalanches could be triggered low on a slope and away from what we think of as traditional ridgeline wind slab start zones.  Wide propagation is possible into connected terrain.  Use conservative decision making and travel techniques.   

Avalanche Discussion

Observations yesterday from Tamarack Peak (Mt. Rose area) showed overall good stability.  Snowpack tests targeting the 12/15 near crust facets showed no weakness and signs that propagation was not likely on this layer.  Recent wind loading and scouring had previously occurred throughout this area with wind scoured snow surfaces and wind effected snow in exposed areas.  No reactive wind slab development was found on multiple aspects with snowpack tests and informal observations.

A snow pit was submitted from above Lake Mary (Donner Summit area) at 7300', NW aspect.  Multiple snowpack tests continued to show weakness above the 12/15 rain crust on near crust facets.  An ECT propagated across the column indicating that propagation is likely if you could triggered this weak layer.   

Regions covered