Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2–3

  Ridgetop winds are on the increase this morning out of the SW and there is still snow on the ridgetops available for drifting.  This blowing and drifting snow will form new wind slabs mainly near treeline and above treeline on NW-N-NE-E-SE aspects. Wind slabs may also form to a lesser extent in below treeline areas due to the strength of the winds.  Wind slab avalanches are expected to be large to very large in size today with human triggering likely. 

  Use blowing snow, wind drifted pillows of snow, cornices above a slope, and wind textured snow surfaces as clues to indicate where unstable wind slabs may exist.  Plan routes that provide a buffer and margin for error when navigating around slopes below cornices and other wind loaded terrain.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  Lots of uncertainty and remaining unknowns here. As the recent storm snow has settled and become a more cohesive slab snow surface cracking into old snow layers and unstable snowpit test results have begun to appear. Faceting along the Jan 4 rain crust and the New Year's upside-down density change have presented some concerning data. If you trigger any snowpack collapses, whumpfing noises, or snow surface cracking, pull back into lower angle terrain and consider avoiding NW-N-NE aspect avalanche terrain in the area.