Central Sierra Nevada

Problèmes avalancheux

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  2–3

  Old, weak, faceted snow lurks below several feet of recent storm snow in parts of the forecast area. These weak layers reached their tipping point over the past few days and have been slow to stabilize. As is often the case with persistent slabs, these weak layers are not always easy to trigger, and snowpit test results can be hit or miss. Reports of continued instability include:

  • One snowboarder caught and carried yesterday in a wide propagating size D3 avalanche on a N to NE aspect around 9,200' near Blue Lakes, south of Carson Pass. This avalanche was triggered during the group's second run on the slope.
  • A snowboarder remotely triggered a size D2 avalanche yesterday near Ebbetts Pass on a N aspect near 9,000'.
  • Multiple other parties reported additional snowpack collapses and whumpfs in the Carson Pass and Ebbetts Pass areas yesterday.

  Backcountry travelers could trigger persistent slab avalanches again today. NW-N-NE-E-facing slopes at elevations near and above 8,000 ft in the eastern and southern parts of the forecast area are the most likely place for more avalanches today. Fewer signs of instability have been reported from the northern and western portions of the forecast area. Below 8,000 ft, rain during the storms mostly destroyed the faceted weak layers of concern or left behind a very strong, thick rain crust above it.

  Day to day improvements in stability are expected, but more slowly and different than when we are dealing with just recent storm snow and no persistent weak layer. If you are traveling to the aspects and elevation range associated with this avalanche problem, it is a good idea to scale back to conservative, low angle terrain selections for now, especially in the southern and eastern portions of the forecast area. Choosing alternate aspects, such as SE-S-SW, is another way to reduce some of the risk.