Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2

  New wind slabs have formed on wind-loaded slopes as a result of new snow and gale force winds. Near and above treeline NW-N-NE-E-SE aspects above 8000 ft where the most new snow has accumulated should hold the largest wind slabs. As snow levels drop today, additional snow and intense, pervasive winds will cause existing wind slabs to grow in size and new wind slabs to form at lower elevations and potentially in some below treeline areas. Large human-triggered wind slab avalanches remain very likely and natural wind slab avalanches are likely. In areas where rain falls on previously wind-loaded slopes, wind slab avalanches could involve wet snow and release more easily.

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2

  Rapidly changing conditions during this storm have allowed weak layers and slab layers to form in the storm snow. Human-triggered storm slab avalanches remain very likely and natural storm slabs are likely. Storm slab avalanches could occur on any steep slopes on any aspect. Most storm slabs would involve the storm snow but some could entrain older snow especially in a few lower elevation areas on E-SE-S-SW aspects where a weak layer may exist near a thin crust. Until snow levels fall, rain falling on storm snow could weaken existing storm slabs and potentially result in larger avalanches that entrain some wet snow. As snow levels fall, new snow accumulation could cause new storm slabs to form at lower elevations.

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1

  Rain falling on snow today will continue to make widespread loose wet avalanche activity very likely. Loose wet avalanches could entrain significant amounts of wet snow and become large enough to bury or injure a person. The rain will also continue to magnify and complicate the other avalanche problems. As snow levels fall today, this problem should start to diminish.