Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Mon
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Expect slabs of wind-blown snow and storm snow to avalanche as heavy snow, some rain, and strong winds continue today. Avalanches could occur on any steep slope at any elevation. Travel in, near, or below avalanche terrain is not recommended.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–3

    New snow and strong wind keep adding layers of wind-blown snow on top of existing wind slabs. Wind slab avalanches are very likely on slopes near ridges, open faces, and gullies. Some may involve the newly formed wind slabs, and some could entrain wind-loaded snow from earlier in the storm. These dense wind slabs could break above a person or after someone gets onto a wind-loaded slope. NW-N-NE-E-SE aspects near and above treeline hold the largest and most reactive wind slabs. A few wind slabs may also lurk in below treeline areas or on other aspects due to the strength of the winds. Large, fragile cornices that can fail far from their edges loom over many slopes. These will keep growing during this storm.  

    Traveling in, near, or below avalanche terrain is not recommended today. If you do get out, give yourself an even larger buffer to avoid avalanche terrain since blowing snow and poor visibility will make it hard to see what terrain may lurk above or nearby. 

    (3/10/2023)

    Looking down on the debris and crown from the avalanche, I remotely triggered when I stepped off my skis near the top of Andesite. This avalanche occurred in a spot that had previously slid. So far, this slope has avalanched and refilled at least twice and maybe three times during this storm.

    Photo: SAC

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    Changing conditions during the storm have left weaknesses in the storm snow, including layers of heavier storm snow on top of lighter layers, graupel layers, and crusts. Unstable storm slabs could exist on any steep slope, even in below treeline areas and other typically sheltered areas. More snow today will allow these storm slabs to grow in size and extent. 

    Areas that people typically think of as "safe" on a storm day may hold unstable storm slab conditions. Traveling on, near, or below slopes steep enough to avalanche is not recommended. 

  • Loose Wet

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

    Near and below 6500 ft, where rain falls on snow, expect wet loose avalanches on steep slopes. Some of these may remain small due to the limited terrain below 6500 ft, but some of them may entrain enough snow to cause problems for people. The potential for larger wet slab avalanches continues to decrease as wet snow from earlier in storm at higher elevations continues to refreeze.

    (3/10/2023)

    Looking up at an avalanche that likely happened Thursday night on Andesite. The debris looked like it had been wet.

    Photo: SAC

Avalanche Discussion

We saw and received more signs of unstable wind slabs yesterday on Donner Summit and in the Mount Rose backcountry. Poor visibility and stormy conditions have limited observations of larger terrain. Many larger slopes have likely avalanched, refilled, and slid again during this storm.  The storm continues to load the snowpack with rain and heavy snow. Some uncertainty exists about how the deep and complex snowpack will react to this large load. Large loading events can produce unexpected outcomes.

Regions covered