Central Sierra Nevada

Lawinenprobleme

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  2

  Human-triggered wind slab avalanches will remain likely today on wind loaded slopes above 8000 ft. where most of the precipitation fell as snow. Some wind slab avalanches may remain possible in lower elevation areas exposed to wind-loading as well. Most wind slabs should exist in near and above treeline terrain on NW-N-NE-E-SE aspects but some could also linger on W aspects due to a more southerly component to the winds during the storm. Wind slab avalanches could be large and destructive. The strong March sun could also make some of these wind slabs easier to trigger on sun-exposed E-SE and W aspects. 

  Use clues like recent wind slab avalanches, shooting cracks, cornices above slopes, ripples, drifts, or other wind created textures to help identify where wind slabs may exist and avoid those slopes in favor of more sheltered terrain or lower angle slopes. 

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1

  Strong March sunshine may provide enough warming for some loose wet instabilities to form on sun-exposed slopes where new snow exists today. If enough warming does occur, rollerballs, pinwheels, and loose wet point releases should comprise the majority of the loose wet instabilities. While most of these wet snow instabilities should remain small, some could entrain enough snow to bury or injure a person. The strong sunshine may also make triggering an isolated lingering storm slab possible today as well.

  Wet sticky surface snow, small pinwheels or roller balls, or recent wet snow avalanches represent some of the clues that warming instabilities are a problem. Avoiding wet snow issues means moving to shaded slopes where colder softer snow is likely to exist. 

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  3

  Deep slab avalanches that fail on the graupel / melt-freeze crust combination buried deep below the surface should have become more difficult to trigger, but some deep slabs may also remain possible today in some specific / isolated areas. East aspects above 9000 ft. in the Mt. Rose backcountry are the most suspect for deep slab activity, but observations prior to the storm found this layer in other places along the Sierra Crest as well. Significant uncertainty exists as to whether or not deep slabs still represent a problem for backcountry travelers. In many areas, this layer should be able to support the new load, but it is possible that in some places it cannot.  Due uncertainty surrounding this problem, deep slabs may be possible on any aspect with an east component (NE-E-SE) above 9000 ft. If a deep slab avalanche does occur today, it would be very large and likely unsurvivable. 

  Due to the combination of uncertainty, a lack of data after the storm loaded the weak layer, and the catastrophic consequences of such an avalanche, deep slabs continue to warrant inclusion as an avalanche problem and avoiding slopes where even a remote possibility of a deep slab may exist is the best choice for today.