Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Gale force winds and new snow will form wind slabs today.  As snowfall increases into the afternoon, more snow will be available for wind transport creating larger wind slabs.  Most of these wind slabs will form in near and above treeline areas, but with wind gusts well over 100mph, wind slabs could also form in below treeline terrain.  Where these wind slabs form on top of the recently buried surface hoar or graupel layers, these wind slabs could be easier to trigger and propagate wider.  Large and reactive wind slabs are expected to form today.

  Blowing snow, cornice formation, new wind pillows, and wind scouring clues should help determine where these wind slabs are forming.  Utilize large safety margins, avoiding or moving around steep wind loaded terrain and areas below large cornices. 

  

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Storm slabs could form today on all aspects in near and below treeline areas.  Snowfall intensity is expected to increase throughout the day with rapid loading this afternoon.  Buried surface hoar, just below the current snow surface, has been found on NW-N-NE aspects along with a more widespread layer of buried graupel.  Either of these weak layers could cause wider propagating and easier to trigger avalanches today.  This avalanche problem is expected to increase throughout the day as more snow accumulates and storm slabs get larger in size.

  Areas that have these weak layers slightly buried below the old snow surface will be the most problematic today.  Shooting cracks or collapsing may be signs that this weak layer exists in your area.  Utilize lower angle terrain and slopes if in doubt of this weak layer and storm slab problem.