Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

High winds today will form thick slabs of wind-blown snow in exposed areas along ridges and in gully features.  Storm slabs remain a concern as more snow continues to add to the existing storm snow totals .  Cautious route finding and conservative decision making are essential while traveling in the backcountry to avoid these avalanche concerns.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    SW winds have been forming wind slabs and building out cornices throughout most of this storm cycle on NW-N-NE-E-SE aspects in near and above treeline areas.  Winds shifted to the NE/E overnight and will be in the strong to gale force range through today over higher ridges and peaks.  These NE winds have large amounts of low density snow to transport today into new wind slabs on SE-S-SW-W-NW aspects in exposed areas.  Wind slabs could be on most any aspect in near and above treeline and even down into some open below treeline areas due to the strong NE/E winds.   Natural wind slab avalanches today are possible.

    Signs of wind slab development would be: recent avalanches, blowing snow, wind pillows, and snow surface clues.  Wind slabs will be developing in different areas than yesterday.  Better snow quality will exist in wind protected below treeline areas that avoids most of this wind slab avalanche problem.    

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    Storm slab avalanche instability has been limited to this point.  Most observations and reports have been of loose dry sluffing in steeper below treeline terrain with little signs of cracking or slab development.  A couple things to think about:  we have received upwards of 3 to 4.5 feet of new snow in the last several days, the NE/E winds will have started to scour some of the new storm snow on exposed slopes and wind stiffen some of this snow in many areas, temperatures are forecasted to warm to near the freezing mark in the 7000-8000' range today and the new additional snow could be heavier than the previous snow.  Some of these changes may cause storm slabs to behave differently today.   Due to the convective nature of this storm cycle, snow totals and avalanche activity can vary widely from one area to the next. 

    Look for cracking in the storm snow as you travel through terrain.  You will need to get off of the existing track to see this.  If you see any indication that cohesion or weakness exists in the storm snow, move to lower angle non-avalanche terrain.

Avalanche Discussion

Recent Observations:

  • Limited observations have been available throughout this storm cycle due to the snowfall intensity, strong winds, and low visibility.  No avalanches have been reported at this point.
  • Layers of graupel, density changes, and potentially some weakness at the new snow/old snow interface below a surface crust have all been found within the recent storm snow.
  • Some layers of old graupel, facets, and/or buried surface hoar can be found about one to two feet below the recent storm snow on some NW-N-NE aspects. For the most part, these layers are well bonded into the snowpack. It is unlikely that the amount of low density new snow load that occurs this week will overload these layers.

Regions covered