Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Snowfall and wind overnight have left slabs of wind-blown snow on the downwind side of terrain features like ridges, gullies, and open slopes. Today's strong winds will keep loading more snow onto these areas despite the decrease in snowfall this morning. These wind slabs may not have bonded to the old crusts, wind-scoured surfaces, and old loose snow below them. The largest and most sensitive wind slabs should exist in near and above treeline terrain, but some wind-affected snow may lurk in below-treeline areas as well. Triggering a wind slab avalanche will be likely today. These avalanches could involve enough snow to bury and injure people. New fragile cornices also likely formed above wind-loaded slopes during this storm. 

  Blowing snow, cornices above a slope, snow drifts, and wind-created textures like ripples in the snow can all help identify where wind slabs exist. Recent avalanches or cracking in wind-blown snow represent obvious signs that the wind slabs are unstable. Still, it is safe to assume many wind-loaded slopes will be unstable today, even if those obvious clues are absent. Traveling in areas sheltered from the wind can help reduce the chances of triggering a wind slab avalanche and increase the chances of finding soft, consistent snow. 

   

  

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Temperatures have steadily cooled during this storm and should have left lighter snow on top of more dense snow. While this may mean the storm snow remains less slabby in sheltered areas, it could still sluff off of the crusts and other firm surfaces below it. The cold soft snow on top could also slide off the more dense storm snow below it. Avalanches of loose snow will be possible on steep slopes in sheltered areas today. Most of these avalanches may remain small, but they can entrain more snow as they move downhill. Some soft slabs may also exist in below treeline areas if the new snow has gotten slightly wind-affected.

  Loose snow avalanches can move quickly once they start and may entrain enough snow to knock a person over or push them off course into higher consequence terrain like cliffy areas or gullies. Pay attention to the terrain around you and avoid areas with terrain traps.