Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

MODERATE avalanche danger will continue in near and above treeline terrain due to the hard wind slabs created by the strong NE winds. While these hard slabs may be difficult to trigger, human-triggered avalanches remain possible today. Identify where wind slabs exist and avoid steep wind-loaded terrain. Firm, scoured, or icy surfaces where arresting a fall would be challenging also exist on exposed near and above treeline terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    The strong E and NE winds since Sunday night have formed hard wind slabs on the wind-loaded W-SW-S aspects and on cross-loaded NW and SE aspects. These wind slabs exist in specific areas in near and above treeline terrain near ridgelines and have grown up to 18 inches in depth. These wind slabs rest on top of an older, looser layer of snow that could serve as a weak layer. Triggering these new wind slabs may be difficult due to the strength of the slab, but it is possible for the right trigger in the right place to cause an avalanche. If they do break, these hard wind slabs would likely break above the person who triggers them. Areas where a shallower wind slab exists, places near exposed rocks, convex rollovers, and unsupported slopes could represent some of the trigger points where breaking one of these hard slabs may be easier.

    Use clues like blowing snow, hollow sounding snow, cornices above slopes, drifted snow, ripples in the snow surface, and other wind created textures to identify where wind slabs may exist and avoid those areas. Travelling in sheltered non-wind-affected terrain where softer snow still exists should provide safer and more enjoyable conditions today. 

Avalanche Discussion

* Hard wind slabs existed on NW aspects on Castle Peak with a weaker layer of snow below them. Tests on these wind slabs yielded unstable results (ECTP's) that indicated that they might be difficult to trigger but if they do break, they could produce avalanches.

* Widespread firm, icy, scoured surfaces existed on exposed N-NE-E aspects on Chickadee Ridge, Basin Peak, and Castle Peak.

* NE winds continued to transport snow away from the N-NE-E aspects and onto the NW-W-SW-S-SE aspects during the day yesterday.

* Soft, unconsolidated snow still exists on near and below treeline northerly aspects sheltered from the E and NE winds. 

Snow coverage is deepest in areas above 8000 ft. in the northern half of the forecast area (north of Emerald Bay). Even at these elevations, snow coverage varies by location. Some areas at the upper elevations south of Emerald Bay still have marginal snow coverage. Below 8000 ft. most areas still have patchy snow coverage with many exposed obstacles and areas of bare ground. 

Regions covered