Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Fri
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Heavy snow and gale-force winds will overload the weak snowpack and create very dangerous avalanche conditions. Widespread, large natural and human-triggered avalanches are very likely in exposed and sheltered terrain at all elevations. Avoid traveling on, below, or near slopes steep enough to avalanche. Avalanches may be triggered from flatter areas below, above, and to the sides of steep slopes.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–3

    1 to 2 feet of new snow will overload the weak, sugary snow (facets), and large avalanches will occur today. Weak snow was widespread before this storm, and these avalanches could occur at any elevation. The most widespread and weakest snow existed on NW-N-NE-E aspects, with some weak snow on other aspects. Once a fracture starts in this weak layer, it can propagate long distances like a falling row of dominos. This domino effect allows avalanches to break wider than expected, wrap around terrain features, and travel farther downhill than usual. People can also trigger these avalanches remotely from nearby slopes or flat areas at the bottom of a slope. 

    Very dangerous avalanche conditions will exist today. The best plan is to avoid traveling in or near avalanche terrain completely. Poor visibility/driving snow will complicate things by making it hard to see the terrain around you and hard to identify avalanche terrain. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    Gale-force winds and heavy snow will pile slabs of wind-drifted snow onto leeward-facing slopes. In some areas, these wind slabs will form on top of weak snow. In this case, they will behave like deeper versions of the storm slabs mentioned above. In other areas, they will land on previously wind-scoured snow surfaces. Either way, large wind slab avalanches will be very likely today. They could run longer than usual or trigger additional avalanches (the storm slabs mentioned above) as they move downhill. The largest and most unstable wind slabs will exist on NW-N-NE-E-SE aspects. 

    As mentioned above, avoiding avalanche terrain and terrain connected to avalanche terrain is the best plan today. This includes flat areas with steeper terrain above them. 

Avalanche Discussion

Before this storm, the snowpack was weak and shallow. Numerous rocks, trees, stumps, and other obstacles existed on the surface or just below the surface. These obstacles will get hidden by today's storm but will likely not be buried deep enough not to hit. They would also increase the consequence of getting caught in an avalanche.

Regions covered