Central Sierra Nevada

Avalanche problems

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1

  Human triggered storm slab avalanches may remain possible in some areas today especially where loose weak old snow (near crust facets) exists above the 12/15 rain crust at the base of the recent snow. As the new snow starts to consolidate, it may start to take on more slab-like properties, and this avalanche problem could start to exhibit more persistent slab characteristics in the coming days in areas where the near crust facets exist and remain weak. In some areas, where very little cohesion exists in the new snow or where the near crust facets do not exist or where the new snow has bonded to the snowpack below it, this avalanche problem may no longer be much of a problem. In other areas, some storm slabs may still linger on any aspects in near and below treeline terrain on slopes steeper than 34 degrees where recent snow exists especially on the NW-N-NE-E aspects where these storm slabs are most likely to rest on near crust facets. Some uncertainty exists concerning whether or not these storm slabs may or may not remain active today, but the possibility that they will warrants careful evaluation of the snowpack and terrain before committing to any slope where storm slabs may exist. Avoiding slopes with potential storm slabs by sticking to lower angle slopes or well-anchored slopes can allow for a more fun and safer day recreating on the snow.

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2

  While triggering a wind slab avalanche should have become more difficult today than yesterday, some human triggered wind slab avalanches may still remain possible on some wind-loaded slopes. Complex and extreme terrain like couloirs, cliffy areas, or unsupported slopes on near and above treeline wind-loaded N-NE-E aspects and the cross-loaded NW and SE aspects represent the best places to find lingering wind slabs today. Some data over the last few days indicates that some wind slabs may have bonded to the old snow, and other data indicates that some have not. In many areas, wind slabs could measure 1.5 to 3 ft in depth with even larger wind slabs on the most wind loaded slopes. If they do break, they could propagate across a slope and could break above the person who triggers them.  

  Use clues like cornices, blowing snow, snow drifts, wind pillows, scoured surfaces, ripples in the snow, and other wind created textures to help determine where wind slabs may exist. Use this knowledge to find terrain without wind slabs to recreate on.