Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2

  Strong winds and more than a foot of new snow have already formed fragile wind slabs on many leeward slopes. These wind slabs will become much larger and more widespread in the next 24 hours with more gale force winds and another few feet of snow forecasted to start later this morning. Near and above treeline NW-N-NE-E-SE aspects will hold the largest wind slabs, but wind slabs could also exist in wind-loaded areas below treeline. In many areas especially along the Sierra Crest, these wind slabs rest on top of weak old snow layers. Failure of these layers could allow remote triggering and/or wider propagation with avalanches possibly wrapping around corners and across adjacent avalanche paths.    

  Triggering a wind slab avalanche will be likely this morning and become very likely this afternoon and during the night. Some large natural wind slab avalanches could become likely as well. Large destructive avalanches could occur. Travel in avalanche terrain is not recommended.

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1

  Rapid accumulation and changing conditions during the storm last night may have left sensitive storm slabs on steep sheltered slopes. More snow starting later this morning and continuing through the night will exacerbate the storm slab problem. In cases where these storm slabs form above old weak snow, they could exhibit some persistent slab characteristics and be easier to trigger and propagate across larger areas when they fail.  

  Storm slab avalanches could become very likely in the next 24 hours especially during times when snowfall rates reach or exceed 2 inches per hour. Travel in avalanche terrain is not recommended.