Central Sierra Nevada

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  It has been 2 full days since our last report of a snowmobiler triggered persistent slab avalanche on Forestdale Divide in the Carson Pass area.  Old weak faceted snow continues to exist below multiple feet of recent storm snow.  Avalanche activity and signs of instability have mostly been focused on the eastern and southern portions of the forecast region, especially in the Carson Pass to Ebbetts Pass areas on NW-N-NE-E aspects above 8000'.  The northern and western portions of the forecast area received more rain during our last storms to help strengthen these weak layers and bridge them with a strong rain crust.  Snowpacks are also generally much stronger and deeper in the northern and western portions of the forecast region.  These faceted weak layers are expected to continue to gain strength on a day to day basis, but these gains and how fast they stabilize will be different area by area.   

  While triggering a large to very large persistent slab avalanche is becoming more difficult, it still remains possible today.  Conservative terrain choices and decision making are the best strategies to manage this avalanche problem if traveling in the areas highlighted above.  Steep complex terrain with multiple trigger points remains some of the most likely areas for these avalanches to occur.  Utilizing simple terrain under 30 degrees in steepness with no overhead hazard or recreating on SE-S-SW aspects where this avalanche problem does not exist would be ways to reduce your exposure to this avalanche problem.

  These weak layers could reactivate with the large storm loading event expected on Thursday and Friday.