Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
View on map

Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
Open full map
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Even though signs of unstable snow have become less obvious, people could still trigger avalanches that break on old, weak snow buried 1 to 3 feet below the surface. These avalanches could come as a surprise and have serious consequences. Carefully assess the snowpack before committing to slopes steep enough for snow to slide down, especially in colder, shaded areas.

This forecast will last for 2 days. The next update will happen on 12/26.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Ingredients for a persistent slab avalanche problem still exist in the forecast area. Sugary snow (the persistent weak layer) buried under more consolidated snow (the slab layer) lingers on many northerly-facing slopes above about 8300 ft in the mountains east of Lake Tahoe. While obvious signs of instability like whumpfs, snowpack collapse, and shooting cracks have decreased, more detailed formal observations produce unstable results daily. Some slopes near and above 8900 ft on the Sierra Crest also show signs of unstable snow.

    As obvious signs of instability decrease, it is easy to assume that slopes have become stable and get lured into a false sense of security. However, persistent slab problems are slow to gain strength and do so in a checkerboard fashion, with trigger points hiding in areas of seemingly stable snow. Persistent slab avalanches remain possible, and triggering an unexpected avalanche may represent the first and only clue of an unstable slope.

    Traveling on slopes where the weak layers do not exist or in lower-angle, non-avalanche terrain can help reduce your chances of getting surprised by this problem.

     

     

Avalanche Discussion

Weak, faceted (sugary) snow still lurks in the lower half of the snowpack on many NW-N-NE aspects above 8000 ft. The moisture content of this weak snow has increased, especially below 9,500'. Weaker and still dry facets have been observed in locations at 9,700' and 9,800'. In the Carson Range, where the weakest snow was reported before the last storm, these moist to wet facets fail in snowpack tests daily. People also triggered slope-scale snowpack collapses on 12/19 and 12/20. Persistent slab problems live up to their name, and this problem may linger for some time or continue to reactivate in future storms.

Snow surface warming occurred across all aspects on Wednesday and Thursday. A crust has formed on the snow surface up to 8,300', potentially higher in some areas due to recent fog.

The snowpack has become more usable, especially above 7,500'. There are still rocks to hit and open creeks to deal with, but not nearly as many as before this last storm.

Regions covered