Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Strong winds will continue to transport snow and form thick slabs of wind-blown snow along ridges and gully features. Strong March sunshine with much warmer temperatures will cause widespread areas of wet snow avalanches on sun exposed slopes.  Conditions are expected to change quickly today-cautious route finding and conservative decision making are essential to avoid these avalanche problems.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Northeast winds have continued in the gale force range overnight with gusts over 100mph over the higher ridges and peaks.  Large amounts of light snow continues to be available for wind transport until these NE winds decrease this afternoon and shift to the W.  These NE winds have scoured exposed terrain and are building out wind slabs on SE-S-SW-W-NW-N aspects in near and above treeline areas, with some wind slabs potentially in below treeline terrain due to the high wind speeds.  Large and reactive wind slabs are likely to exist today with natural avalanches possible.

    Look for clues like recent avalanche activity, blowing snow, new cornice formation, and snow surface clues as to where these wind slabs will be forming.  Snow surface cracking in wind loaded terrain will also be a sign of unstable snow.  Wind slabs on slopes that receive intense solar radiation may weaken and fail easier today.  Traveling in more wind protected below treeline areas could provide better snow quality and minimize some of this avalanche problem.     

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Widespread wet loose avalanches are expected to occur today!  Strong March sunshine and well above freezing temperatures will change the snow surface on sun exposed slopes quickly.  Deep unconsolidated snow exists post storm and will quickly weaken during this warmup starting this morning.  Up to size D2 wet loose avalanches could occur.  Larger slopes will have the potential to produce these larger avalanches that could run long distances.    

    Roller balls, pinwheels, and small point releases will be signs the snow surface is wet and loosing strength.  Once the snow surface becomes wet and heavy, it's time to move away from avalanche terrain or change aspects away from the sun.  Tree drippings and tree bombs will occur on all aspects as rapid warming occurs today. 

Avalanche Discussion

Recent Observations:

  • Large natural avalanches occurred on Tuesday evening in unmitigated areas that affected infrastructure.  Another large avalanche was reported from Hidden Peak, West Shore area that is thought to have occurred in the same late Tuesday night timeframe.  No avalanches were reported that occurred on Wednesday.
  • Intense blowing snow continues in near and above treeline areas over the past three days. Some blowing snow was observed in open areas below treeline as well. 
  • The Feb 21 old snow/storm snow interface is now buried 6 to 10 feet deep in the snowpack in wind protected areas on some NW-N-NE aspects.  Some snowpack tests have shown weakness on this layer, but other signs of instability have not been present for multiple days now.  Due to the depth of this layer, the strength of the snow above, and the relative strength of the layer-avalanches are unlikely on a regional scale.

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