Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Avalanche danger will increase to considerable today due to wind slab, storm slab, and loose wet avalanche problems.  These avalanche problems will be likely in below treeline, near treeline, and above treeline terrain.  Dangerous avalanche conditions will exist throughout today.  Natural avalanches will be possible and human triggered avalanches will be likely.  Conservative decision making and cautious route finding are essential.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    Wind slabs will be likely on NW-N-NE-E-SE aspects near and above treeline as new snow and gale force SW winds impact our area today.  These wind slabs will continue to grow throughout the day and will be large enough in size to injure or bury a backcountry user.

    Look for clues to where wind slabs are forming such as blowing snow, cornice formation, and wind pillows.  Avoid terrain with new wind slab development.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    As snowfall intensity increases this morning, storm slabs will become likely on all aspects in below treeline and near treeline terrain.  Snow levels are generally forecasted to drop throughout the day but an upside down storm snow structure could exist in many areas.  In isolated open below treeline terrain, there remains the possibility that surface hoar has been buried under the recent storm snow.  If this occurs, easily triggered avalanches would be likely on lower angle slopes.  

    Look for clues such as snow surface cracking and avoid areas where unstable snow exists.   

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    Areas of rain on snow today will be prone to loose wet avalanche activity. This is most likely to occur below 8000' on slopes steeper than 35 degrees and should diminish as snow levels are forecasted to drop to near 6000' later this morning.  Loose wet avalanche activity today could be either natural or human triggered. Terrain traps such as creek beds and road cuts could increase the depth of avalanche debris associated with otherwise small loose wet avalanches.

Avalanche Discussion

Observations were made yesterday on Andesite Peak (Donner Summit area).  Small storm slabs and winds slabs were forming throughout the morning hours in this area and were able to be intentionally triggered.  3 to 5'' of new storm snow existed in this area.  Temperatures and snow levels were rising throughout the morning creating an upside down storm snow structure with heavier storm snow on top of lighter snow.  Loose wet avalanches were observed on the drive to the trailhead at elevations below 7200'.  Buried surface hoar was not found in many open below treeline locations in this area. 

Regions covered