Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2–3

  Intense blowing snow and wind slab avalanches have occurred over the past two days. Ongoing winds today combined with the addition of high intensity snowfall above 7,000' to 7,500' will further increase the hazard. Wind slab avalanches are expected today 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 could be very large in size today and run down into below treeline terrain and areas of mature timber.

  Travel in, near, or below avalanche terrain is not recommended at this time.

  

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Snowfall rates of 2 to 4 inches per hour lasting until around noon today are expected to deposit new snow faster than it can bond to itself and the old snow surface. Slabs of unstable storm snow are expected to form today above the rain/snow line in wind protected areas on all aspects.

  If attempting to navigate in low angle, non-avalanche terrain in wind protected areas below treeline today, take great care not to wander into areas with steeper avalanche terrain above. Natural avalanches from above could easily travel down into lower angle terrain today and into treed areas.

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  Faceting along the thin Jan 4 rain crust and unstable snowpit test results have been reported from NW-N-NE aspects in the 7,500' to 8,500' elevation range in the Border Ruffian and Blue Lakes areas south of Carson Pass. The first avalanche on this layer may have occurred yesterday. Observations targeting this layer at various elevations in the Independence Lake, Donner Summit, Pole Creek, Mount Rose, and West Shore Tahoe zones have not revealed any faceting or weakness on this specific layer. Substantial unknowns remain in regard to the areas where this layer is weak and problematic.

  In any areas where this layer is weak and problematic, it is currently receiving stress from a load of new snow and possibly rain during the current storm cycle. An avalanche that fails on this crust/facet layer would fail at a minimum of 2 to 3 feet deep in the snowpack, likely have wide propagation, and could be triggered from low on a slope or from the side. Travel in, near, or below avalanche terrain is not recommended at this time.