Central Sierra Nevada

Avalanche problems

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2

  Deep loose wet snow exists on all aspects and at all elevations due to significant rainfall over the last 24 hours saturating the snowpack in many places. The rain will continue today and it will continue to weaken the snowpack. Loose wet avalanches will be likely today on any steep slopes. Northerly aspects and higher elevation slopes that have experienced less robust melting during the warm weather will be more likely to hold larger loose wet instabilities. Wet snow instabilities could include pinwheels, rollerballs, and loose wet avalanches. Some of the loose wet avalanches could involve large amounts of wet snow and could be large enough to bury or injure a person or maybe even a car.

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  3

  The rain has added significant load to the existing snowpack while melting bonds and significantly weakening the snowpack at the same time. The decreased strength should make it easier to trigger the deeply buried Feb. facet weak layer and the added weight may be enough overload that weak layer. As a result, large deep slab avalanche activity is possible today on NW-N-NE aspects especially in areas that did not avalanche during the previous deep slab avalanche cycle. In addition rain saturated weak snow may allow some deep wet slab avalanches to occur on other aspects especially in areas where the snowpack rests on surfaces like granite slabs. Natural deep slab avalanches are possible today. Any slab avalanches that occur today could be large and destructive and would involve heavy wet snow.

  This kind of avalanche problem is difficult to predict and a high amount of uncertainty is associated with it. What is certain is that if one of these avalanches does occur and a person is invovled, the consquences would be very serious. Due to the combination of severe consequences and high uncertainty backcountry travel in avalanche terrain or in the runout zones of steep slopes is not recommended today.

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1

  If snow level drops before the precipitation stops, some higher elevation areas could recieve enough snow for small wind slabs to form near ridgelines on leeward aspects by this afternoon. Leeward slopes above 9000 ft. hold the best postential for some wind slab formation. If wind slabs do form, some human-triggered wind slab avalanches may be possible in the most heavily wind-loaded areas. 

  Identify where wind slabs may exist using clues like active wind-loading, cornices above slopes, drifted snow, ripples in the snow, and other wind created textures then avoid the wind slabs in favor of more sheltered terrain.