Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
View on map

Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
Open full map
Out of date — this forecast expired 11 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Considerable avalanche danger exists on all aspects and elevations today on slopes steeper than 32 degrees.  Wind slabs and storm slabs have been forming since yesterday and will continue to grow in size and sensitivity.  Storm slabs have shown the possibility for remote triggering and propagation across long distances.  Natural avalanches are possible and human triggered avalanches are likely today.  Dangerous avalanche conditions exist, cautious route finding and conservative decision making are essential today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    3

    Wind slabs formed yesterday on NW-N-NE-E aspects that were naturally and human triggered throughout the forecast area.  These wind slabs will remain sensitive today and will grow in size as our next storm impacts our region.  Winds will be South in the strong to gale force range and will switch to the Southwest in the afternoon and increase in speed.  8 to 16'' of new snow is forecasted for areas above 7000' throughout today and tonight.  These winds slabs will grow in size up to 2 to 4' deep and be located above treeline and near treeline on NW-N-NE-E-SE aspects.  If forecasted wind speeds materialize, wind slabs could also form in open areas in below treeline terrain.

    Adjust your travel plan to avoid wind loaded areas.  Look for areas of blowing snow, cornice formation, wind pillows, and snow surface clues to help identify where wind slabs are located.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Several areas throughout the forecast region saw storm slabs failing at the new snow/old snow interface in near and below treeline terrain yesterday.  These storm slabs were avalanching both naturally and by skier triggering.  The bonds at this old snow/new snow interface have not had sufficient time to gain strength overnight.  Expect larger storm slabs today on all aspects near treeline and below.  These storm slabs could have the ability to propagate far distances, be remotely triggered, and run through below treeline terrain.  These storm slab may exist on some slopes but not on others depending on the strength of the old snow surface. 

    These types of storm slabs may exhibit unusual behavior for our region and will require extra caution and more conservative travel planning.  Terrain viewed traditionally as "safe below treeline terrain" could be suspect today.  Avoid steeper slopes and terrain traps near or below treeline.  Use small, inconsequential test slopes to gather information.  Look for any cracking or signs of slab cohesion as clues for storm slabs. 

     

Avalanche Discussion

Natural and human triggered avalanches were reported throughout the forecast area yesterday due to wind slab and storm slab instabilities.  On Andesite Peak (Donner Summit) and Becker Peak (Echo Summit) near and below treeline storm slabs were observed.  These storm slabs were failing at the old snow/new snow interface and propagating long distances.  On Silver Peak (Pole Creek) there was storm slab development in near and below treeline terrain.  Wind slabs were sensitive and easy to intentionally trigger along ridgelines.  On Frog Lake Cliffs (Carson Pass) and Powderhouse (Luther Pass) weather and snow amounts were more variable and signs of unstable snow existed.

Regions covered