Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

New snow and wind have created dangerous avalanche conditions in the backcountry. Unstable slabs of wind drifted snow (wind slabs) have formed in lee areas in near and above treeline terrain. Softer slabs of storm snow (storm slabs) may exist on more sheltered terrain. Human-triggered avalanches are likely today. CONSIDERABLE avalanche danger exists near and above treeline with MODERATE avalanche danger below treeline.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Strong SW winds and new snow built slabs of wind drifted snow on leeward aspects during the night. The wind-loaded N-NE-E aspects and cross-loaded NW and SE aspects in near and above treeline terrain represent the most likely places to find fragile wind slabs. These wind slabs will continue to grow in size and extent today as more snow and wind impact the forecast area. Human-triggered wind slab avalanches large enough to bury or injure a person (size D2) are likely today on steep wind-loaded slopes. Natural wind slab avalanches will also be possible today. In addition to the wind slabs on the slopes, large fragile cornices will exist above many slopes. 

    Blowing snow, cornices above a slope, wind pillows, snowdrifts, ripples on the snow surface, and other wind-created features can help identify where unstable and dangerous wind slabs may exist. Avoiding steep wind-loaded areas in favor of more sheltered terrain and lower angle slopes will help limit your exposure to wind slab problems and could provide more consistent snow conditions. 

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Human-triggered storm slab avalanches may be possible today on steep slopes. These kinds of avalanches could fail within the storm snow or near the base of the storm snow. In areas that have received the most new snow or in places where terrain traps magnify the consequences of an avalanche storm slabs could involve enough snow to bury or injure a person. 

    Recent avalanches, cracks in the snow, test slope failures, and feeling for softer snow under more dense snow are clues that storm slabs could exist. Storm slabs tend to exist in areas that people gravitate towards during storms like steep slopes with nicely spaced trees or on steep but sheltered open slopes. Evaluate areas for any signs of storm slab instability before committing to a steep slope. Traveling in lower-angle terrain can still provide great recreation and can help avoid potential instability.  

Avalanche Discussion

* Variable conditions were observed around the forecast area prior to this storm. Some cold soft snow still lingered on shaded and sheltered N aspects. Melt-freeze crusts existed over softer snow on sun-exposed slopes. Areas near ridgelines and on exposed upper elevation slopes held wind-scoured and wind-sculpted snow surfaces.

* In most places, observations have not revealed signs of potential weak layers or instability below the surface of the snowpack. In higher elevation terrain near Luther Pass, the Feb rain crust has weakened and faceted. Some snowpit tests have produced unstable results in this area.

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