Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

CONSIDERABLE avalanche danger will exist through the morning and into the afternoon due to wind slab, storm slab, and deep slab avalanche problems.  As the storm intensifies this afternoon, avalanche danger will rise to HIGH and continue overnight.  Dangerous avalanche conditions will exist with large and destructive avalanches possible.  Travel in avalanche terrain is not recommended.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2

    Snow this morning with gale force SW winds will quickly form new wind slabs on NW-N-NE-E-SE aspects in near and above treeline terrain.  These wind slabs will form above the rain/snow line which could be as high as 7500-8000' initially before snow levels drop sometime this afternoon.  Widespread natural wind slab avalanches will become very likely this afternoon and through the night. 

    Look for blowing snow, cornice formation, and wind pillows as clues to where wind slabs exists.  Avoid steep wind loaded terrain and areas below large cornices. 

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    Storm slabs will be likely on all aspects in near treeline and below treeline terrain.  Initially, these storm slabs may have wet slab and/or loose wet characteristics mainly below 8000' due to heavy rain on snow today.  As the storm intensifies this afternoon and snow levels drop, storm slabs from high intensity snowfall will become likely.  Storm slabs will continue to grow larger as this storm has the potential for 2' of snow by Monday morning along the Sierra Crest.  Natural storm slab avalanches will be likely today and tonight.

     

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Deep slab avalanches will be possible on NW-N-NE-E aspects in both above and below treeline areas.  Buried surface hoar and crust/facet layers are buried 4 to 6'+ deep in the snowpack.  Snowpack tests continue to show that these weak layers could propagate if an avalanche could be initiated.  Triggering one of these deep slab avalanches may be difficult due to the depth of the weak layer, but consequences would be very high.

    Natural deep slab avalanches that are large and destructive will be possible today.  Managing terrain is critical by choosing simple terrain that is not capable of producing large avalanches. 

Avalanche Discussion

*  Several recent small avalanches were observed yesterday on English Mtn. (Independence Lake area).  These appeared to be from the recent rain on snow event.

*  Snowpack tests targeting the buried surface hoar layer showed unstable results at Chief Creek (Pole Creek area).  The buried surface hoar layer was down about 4' deep.

*  Observations from Meadow Lake (Independence Lake area), Tamarack Peak (Mt. Rose area), Chief Creek (Pole Creek area), and Trimmer Peak (Luther Pass area) all showed wet surface snow from the recent high elevation rain/misting event. 

 

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