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

MODERATE avalanche danger is expected today for all elevations due to newly formed wind slab, storm slab, and possible wet loose avalanche problems. Avalanche activity is most likely to occur on slopes 35 degrees and steeper but could occur on lower angle slopes down to 30 degrees in some areas, especially below treeline. Increasing avalanche danger is expected late tonight into early Friday morning with CONSIDERABLE danger to possibly HIGH danger occurring overnight.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Moderate to high intensity snowfall and S winds this morning will create new wind slabs in near and above treeline terrain. The S wind direction versus the more common SW storm wind direction will create a different wind slab distribution than usual today. The vast majority of wind slab formation is expected on W-NW-N-NE-E-SE aspects, but could occur in some areas on S and SW aspects as well. Wind slabs could easily reach a foot or so thick today in the more efficiently wind loaded areas.

    Use clues such as blowing snow, new cornice formations, and newly formed wind pillows to identify and avoid slopes with likely wind slab development.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Fairly high intensity snowfall this morning will create storm slabs in wind protected areas near and below treeline. In some but not all of the large below treeline open areas there is a chance that these new storm slabs are sitting on top of surface hoar which persisted at the old/new snow interface. Anywhere where this is the case, storm slabs will be very easily triggered and avalanches could occur on lower angle slopes down to around 30 degrees.

    Look for clues such as snow surface cracking in low angle terrain for indications where unstable storm slabs exist. Keep in mind that areas with problematic surface hoar could exist on some slopes but not others nearby. This means that observations of stability on one slope will not necessarily apply to an adjacent or other nearby slope in the area.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Areas of rain on snow today, especially new snow will be prone to wet loose avalanche activity. This is most likely to occur below 6,500' to 7,500' on slopes steeper than 35 degrees. Wet loose avalanche activity today could be either natural or human triggered. Terrain traps such as creek beds and road cuts could magnify the depth of avalanche debris associated with otherwise small wet loose avalanches.

Avalanche Discussion

Recent observations from around the forecast area over the past several days have indicated that the existing snowpack is well consolidated and have revealed no problematic weak layers deeper in the snowpack. A few areas of surface hoar were noted to persist yesterday afternoon in large open areas well below treeline. Old snow surfaces generally consist of melt freeze crust on SE-S-SW aspects and well settled but still unconsolidated snow on NW-N-NE aspects.

Regions covered