Central Sierra Nevada

Problemi valanghivi

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Possible

  Dimensione

  2–3

  Backcountry travelers had close calls with very large (size D3) persistent slab avalanches both yesterday and the day before. Old, weak, faceted snow lurks below several feet of recent storm snow in parts of the forecast area. These weak layers recently reached their tipping point 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:

  • A snowmobile triggered avalanche occurred Sunday along the Forestdale Divide on a slope with numerous previous tracks on it. This was a N to NE aspect slope around 9,300'.
  • One snowboarder was caught and carried on Saturday 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 Saturday 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 both Saturday and Sunday.

  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 (especially Carson Pass to Ebbetts Pass) 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 them.

  Over the past two days, several hundred or more backcountry travelers entered avalanche terrain within the forecast area, and three large to very large avalanches were reported. While continued slow day to day improvements in stability are expected, it only takes one large isolated avalanche to disrupt your day or worse.

  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.