Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 13 years ago.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

Highlights

MODERATE avalanche danger still persists on near treeline and below treeline NW-N-NE aspects on slopes 32 degrees and steeper due to lingering persistent slabs.

Human triggered avalanches remain possible. Due to the shallow snowpack any avalanches that do occur would drag people through and into obstacles like rocks, stumps, and other hard immobile obstacles.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    A persistent weak layer (the Dec. 7th facets) with a slab layer above it still exists on near and below treeline NW-N-NE aspects. Human triggered avalanche activity remains possible on these slopes. People can trigger these kind of persistent slabs remotely while standing in low angle terrain or on ridgelines or anywhere that the snowpack under their feet connects to steeper and/or deeper terrain because fractures can travel through the persistent weak layer. 

    Any of these avalanches that do occur would drag a person through rocks, stumps, trees, and other obstacles because of the shallow snowpack and the fact that the near and below treeline terrain holds the most unstable snow.

Avalanche Discussion

Yesterday near Red Lake in the Carson Pass area (photos, videos, snowpit, more info), widespread whumpfing and collapsing continued to occur as the layer of weak sugary snow (Dec. 7th facets) near the bottom of the snowpack broke under the weight of a person on the slope. The more recent snow above has warmed and consolidated into a more cohesive slab layer. In addition to the collapsing and whumfing, snowpit tests also indicated that the current snowpack structure remains unstable and that fractures can travel along the Dec. 7th facets. Yesterday's data came from a spot where previous observations (on 12/12 and 12/9) also showed similar signs of instability. These three observations indicate a very persistent weak snowpack in which the weak layer is NOT gaining much if any strength.

Barely covered rocks, stumps, logs, and other hard, immobile, season-ending, equipment-breaking objects still exist on all slopes. The shallow snowpack does not have enough structure or strength to keep a person above all these things. It only camouflages their existence.

Regions covered