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

Unstable snowpack conditions will continue today.  A mix of wind slab, persistent slab, and loose wet avalanche problems will exist.  MODERATE avalanche danger will continue at all elevations.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Gale force SW winds continued through yesterday transporting snow at the higher elevations.  Below 8500', limited available snow remained for wind transport as warm and wet conditions on Tuesday left wet surface snow and breakable crusts on most aspects.  Above 8500', active snow transport continued with signs of recent wind slab avalanches.  Winds became light overnight and shifted to the NE, they are forecasted to increase this morning with moderate gusts before returning back to light.

    Look for signs of previous blowing snow, cornice formation, and wind pillows.  These wind slabs will be dense and could be stubborn to trigger.  Increased warming today could make cornices more fragile.   

     

     

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    Isolated persistent slab avalanches continue to remain a concern throughout the forecast region.  A layer of buried surface hoar sits 1 to 3 feet deep below the snow surface.  Weak layer stabilization is occurring at different rates at different locations, with some areas still showing signs that this weak layer can propagate and cause an avalanche.  On a regional level, these avalanches have become unlikely, but not impossible.  The last persistent slab avalanche occurred 3 days ago on Monday of this week.

    These persistent slabs exist on NW-N-NE aspects at all elevations.  An avoidance strategy could utilize slope angles below 30 degrees, pick aspects where the problem does not exist, and avoid terrain connected to where this problem might exist.  Complex terrain with multiple trigger points and areas where other avalanche problems could step down to this persistent weak layer remain potential locations for these avalanches to occur.   Avalanches associated with this weak layer would be large with dense heavy slabs of snow.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Loose wet avalanches could form today as daytime warming occurs.  High sun angles and intense April sunshine will warm the snow surface on all aspects and elevations throughout the day.  After a good refreeze of the snowpack overnight, snow surface conditions will melt quickly with warmer daytime temperatures and mostly light winds forecasted for today.  Rollerballs and pinwheels will be an indicator that larger loose wet avalanches are possible.   

Avalanche Discussion

Observations came in from Red Lake Peak in the Carson Pass area yesterday.  Gale force SW winds with intense snow transport was observed over the higher peaks in this area.  Recent avalanche activity was observed in some of these wind loaded areas.   

Observations from Carpenter Ridge (Independence Lake area) showed breakable crusts from a warm and wet Tuesday.  Blowing snow was limited due to the wet or firm snow surface.  Mixed results were seen on the buried surface hoar layer along with unreactive wind slabs.

Regions covered