Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2

  Lingering wind slabs from our recent storm could remain reactive today to human triggering.  Wet heavy snow along with gale force winds during this last storm built out large wind slabs and cornices on NW-N-NE-E-SE aspects in near and above treeline terrain.  These wind slabs could remain reactive today and be large in size.  Wind direction has shifted overnight to the N/NE.  While forecasted to remain light through tonight, elevated NE winds could form new wind slabs on S-SW-W aspects in above treeline areas if winds increase in speed.   

  Look for signs of blowing snow, large cornices, snow surface scouring, and wind pillows.  Avoid areas under large cornices and wind loaded terrain. 

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2

  Buried surface hoar has been reported at multiple locations throughout the forecast region and exists in some places below the recent 12/6-12/8 storm snow.  This buried surface hoar layer has shown unstable snowpack test results and whumpfing sounds.  Uncertainty exists about how widespread and reactive this layer could be.  No known avalanches on this layer have been reported at this point.  This weak layer has been found in open areas in below treeline terrain above 8000'.  Avalanches associated with this layer would involve all the recent storm snow, 1 to 2 feet.  Whumpfing, cracking, or recent avalanche activity in similiar areas would be a sign that this layer is present and reactive.