Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Slabs of wind drifted snow (wind slabs) could be encountered on any aspect today in above treeline and near treeline terrain. Any wind exposed slopes that are not scoured to ice are suspect. MODERATE avalanche danger exists above treeline and near treeline. LOW avalanche danger exists in wind protected areas below treeline. Avalanche danger is expected to increase at all elevations tonight into tomorrow as the next storm system moves through the area.

Avalanche problems

  • Wind Slabs

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

    Ridgetop winds were stronger than forecast yesterday out of the NE, redistributing and drifting substantial amounts of new snow on the ground in some areas. Wind slabs are an ongoing concern today in locations where drifting snow has deposited. These wind slabs could exist on any aspect due to winds shifting between NE and SW. Avalanche size at D1 is most likely with the isolated potential for a size D2 in the most heavily wind loaded areas for most of today. Potential avalanche size is expected to increase overnight into tomorrow with additional snowfall and wind.

    Basically, any slope in above treeline or near treeline terrain that is not scoured down to ice is suspect. Slopes either directly below or adjacent to cornices and wind pillows are the most suspect. Move around these areas with caution, especially if signs of instability such as snow surface cracking or recent avalanches are present.

    Touchy wind slab yesterday on W aspect test slope of Andesite Ridge. Additional shooting cracks occurred up to 30 ft ahead of the skier in this photo.

Avalanche Discussion

* Unstable wind slabs were observed yesterday on W aspects along Andesite Ridge (Donner Summit area) where wind drifted snow was depositing. Numerous shooting cracks up to 30 feet long and a small intentionally triggered avalanche had touchy reactivity. These wind slabs were failing at the interface where the slab of wind drifted snow had deposited on top of the recent new snow, not down on the prominent crust below.

* The Dec 11 layer of faceted snow in the lower portion of the snowpack is being monitored for the possibility of a deep slab avalanche problem if the potential major snowfall event currently slated for Tues-Thurs verifies as forecast.

* It is possible that surface hoar formed last night in wind protected areas on open slopes. If you see surface hoar today that shows signs of lasting until burial tonight, please take a photo and submit an observation to tell us about it.

Regions covered