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

Fresh slabs of wind drifted snow and fragile cornices should start to form in near and above treeline terrain today due to strong winds transporting old snow and new snow accumulation. In addition to these new wind slabs, an unlikely but not impossible deep slab problem still may exist on some isolated near and below treeline slopes. MODERATE avalanche danger exists at all elevations.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Increasingly strong winds from the SW should be able to move any remaining soft snow near ridgelines from the windward aspects to the leeward aspects. New snow today will provide additional material for these wind slabs. Expect to find fresh slabs of wind drifted snow on wind-loaded and cross-loaded NW-N-NE-E-SE aspects in near and above treeline terrain today. These new wind slabs should start out small and grow in size and distribution as more snow and wind impact the region. Wind transport will also build fragile cornices along ridgelines.

    Identify where wind slabs exist using clues like blowing snow, cornices above a slope, scoured ridges, and wind drifted snow. Slopes in more sheltered areas should hold more consistent snow conditions. 

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    No reports of new deep slab avalanches came in yesterday. Observations targeting the weak layer buried below the recent storm snow continue to indicate that triggering deep slab avalanches has become unlikely on a regional scale. Still, human-triggered deep slab avalanches have occurred this week and some uncertainty exists surrounding this problem. Unlikely does not mean impossible and this problem still warrants consideration.

    In the unlikely event that one of these does occur it would be on an isolated terrain feature on a NW-N-NE aspect in near or below treeline terrain where the weak layer exists. Pay particular attention to areas of steep and complex terrain or steep unsupported slopes. Larger triggers like cornice failures or multiple people on a slope or smaller triggers that hit the right trigger point would be more apt to release an otherwise unlikely deep slab. If you have any doubts about the potential for a deep slab, go ahead choose a different aspect or more conservative terrain.

Avalanche Discussion

Observers reported widespread surface hoar on Ebbetts Pass, Talking Mountain, Mount Tallac, and Tamarack Peak yesterday. As light snow started to fall on Talking Mountain, in the afternoon the surface hoar was still intact. 

Yesterday, snowpit tests near a deep slab avalanche that occurred on 3/21 on Powderhouse Peak as well as snowpit tests from Ebbetts Pass, Talking Mountain, Janine's Peak all found the buried crust/facet combo at the base of the recent snow. These tests also indicated that breaking this layer continues to become more difficult. No other signs of instability concerning the deep slab problem or new deep slab avalanches were reported yesterday.

Observers did see signs of warming snow including small roller balls and some small loose wet point releases on sunny slopes on Tallac, around Ebbetts Pass, and on steep sunny S and SE facing road cuts in the Mount Rose area. Wet heavy snow was also reported on southerly aspects of Talking Mountain and Powderhouse Peak yesterday afternoon. 

Regions covered