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

Above 8000 ft. on slopes 32 degrees and steeper, human-triggered avalanches remain possible on NW-N-NE aspects in all terrain and on near and above treeline E-SE aspects. MODERATE avalanche danger exists in these areas due to wind slabs and possible persistent slabs. Higher elevation slopes with the most snow represent both the most dangerous places to go and the places where people want to recreate. Don't let early season excitement overrule good judgment and decision making.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    New snow and strong winds continue to load the leeward slopes. The wind slabs on these slopes continue to grow in size and extent. The new snow and wind has also created large and fragile cornices above the wind-loaded slopes. Human triggered wind slab avalanches large enough to bury or injure a person remain possible today on the wind-loaded N-NE-E aspects and on the cross-loaded NW and SE aspects above 8000 ft. These slabs will become larger and more fragile as elevation and snow depth increase.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Weak layers of sugary snow (facets) exist near the base of the snowpack on northerly aspects above 8000 ft. in many areas. In some areas below 8800 ft. the warmer weather and wet snow/rain has allowed these weak layers to start to gain strength so that they can support the heavy snow above them. However, not enough data exists to say that this strengthening has started to occur everywhere these persistent weak layers remain. Slopes with these weak layers remain suspect especially at higher elevations where temperatures remained colder and all of the recent precipitation fell as snow. Observations like slope cuts and previous tracks are not reliable indications of stability when dealing with persistent slabs. Avoiding areas where these layers might exist or sticking to lower angle slopes without steeper terrain above them are the only mitigation options for persistent slabs. Any other technique is just rolling the dice.

Avalanche Discussion

Yesterday on Caslte Peak, Grouse Rocks, and on Tamarack Peak snow levels seemed to fluctuate between 7400 ft. and 8400 ft. Water had formed in every layer of the snowpack on Castle Peak as high as 8800 ft. making the old persistent weak layers start to stick together. Tests on these layers in the Castle Peak area and snowpit data from 8100 ft. near Grouse Rocks did not reveal signs of instability on these older weak layers. However, in the Tamarack Peak area at higher elevations some collapsing did occur on a NE aspect. It remains unknown whether or not these collapses resulted from the old persistent weak layers near the base of the snowpack failing.

Ski cuts and freezer-sized cornice pieces dropped on wind-loaded test slopes on Castle Peak did not cause any noticable cracking or collapsing on the wind-loaded test slopes.

Regions covered