Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Sunny skies and warmer temperatures are expected for today.  Human triggered avalanches are possible due to wind slab, persistent slab, and loose wet avalanche problems.  MODERATE avalanche danger continues at all elevations.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Strong NE/E winds have continued overnight and are forecasted to remain strong through today.  Wind slab avalanches will remain possible in near and above treeline areas.  Areas that received the most snow yesterday could have larger and more problematic wind slabs today. 

    Look for blowing snow, cornice formation, and wind pillows.  Avoid steep wind loaded terrain.  Rapid warming could further decrease the strength of these wind slabs today.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    Persistent slab avalanches remain a concern throughout the forecast region.  Some snowpack tests continue to show weakness on the old snow crust layer buried 1 to 3’ deep.  While this problem is isolated, there may still be some areas that remain unstable enough for human triggered avalanches today.  The last known avalanche on this weak layer was 2 days ago on Wednesday.  This problem seems to be lingering in higher elevation terrain like the Mt. Rose area, although it has been previously found in other areas.  Avalanches associated with this weak layer could be large ( 1 to 3' deep), propagate wide, and be remotely triggered.    

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    Intense April sunshine and warming temperatures will make loose wet avalanches likely on all aspects and elevations.  New snow from yesterday will warm and become wet quickly this morning.  Widespread loose wet activity will begin with this new snow this morning and then could involve the older snow as crusts soften and weaken with daytime warming.  Rapid warming today could also cause large cornices to become weaker and break off. 

    Roller balls and pinwheels will be indicators that the snow surface is rapidly warming and losing strength.  Once the snow becomes wet and sticky, it’s time to change aspects or call it a day.  Avoid terrain below large cornices and avalanche paths as daytime warming occurs.  Loose wet avalanches could be large enough to injure or bury a backcountry user.

Avalanche Discussion

Observations were done on Relay Peak yesterday to gather more details about the skier-triggered avalanche that occurred there Wednesday, April 8.  They found that the deepest spot of the avalanche had failed on a thin layer of weak snow below the new snow.  The crust at the base of the recent snow was barely discernable.  Several snowpit tests at the crown all yielded unstable results on that weak layer.

Homewood Ski Patrol reported an avalanche from uncontrolled terrain on Qual Face.  A loose wet avalanche from a ski cut stepped down to a deeper weak layer causing a large D2 avalanche.

Regions covered