Central Sierra Nevada

Problemi valanghivi

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Possible

  Dimensione

  2

  Slabs of wind drifted snow and fragile cornices still exist on many leeward facing slopes, and today's new snow and wind today will allow them to grow a little larger. In many areas, these wind slabs have become slightly more difficult to trigger. However, human-triggered wind slab avalanches will remain possible today. Some of these could still break several feet deep and could involve enough snow to bury a person or a car (D2-D3). Wind-loaded N-NE-E aspects and cross-loaded NW and SE aspects in near and above treeline terrain will hold the largest of these wind slabs.

  Signs that a wind slab may exist on the slope below included snow blowing onto that slope, smooth pillows of wind drifted snow, and cornices hanging over the slope. Traveling on more sheltered slopes where wind slabs don't exist will provide softer less wind affected snow as well as limiting your exposure to potentially unstable wind slabs. 

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilità

  Possible

  Dimensione

  2

  In some areas, weak sugary snow existed just below the snow surface on near and below treeline NW-N-NE aspects prior to this storm. In other areas, the old snow surfaces were so hammered that this layer is discontinuous. Now that 3 to 5 feet of storm snow rests on top of this old weak snow, it is hard to tell where the old weak snow may be problematic. So far the only avalanche activity reported on this layer has occurred outside the forecast area to the south. Still, evidence and observations from within the forecast area suggest that large deep slab avalanches may be possible. They could occur in below treeline areas on slopes without a history of frequent avalanches.

  Getting caught in a deep slab avalanche would have severe consequences and may not be survivable. Recent avalanches, whumpfing, or snowpack collapse can indicate potential deep slab instability, but these signs are not always present. Probing into the snowpack or digging a snowpit can also help determine if the weak layer exists. If you find the layer or have any uncertainty about whether or not it exists, choosing a different aspect or more conservative terrain can help avoid this problem.