Central Sierra Nevada

Lawinenprobleme

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Very Likely

  Größe

  2

  Strong winds, intense snowfall rates, and significant new snow accumulation will create wind slabs on leeward slopes in near and above treeline terrain. The largest of these wind slabs will exist above 8000 ft. where more of the precipitation has fallen as snow, but some could form at lower elevations as snow starts to accumulate in these areas today.  Most wind slabs should exist on NW-N-NE-E-SE aspects but some could also form on W aspects due to a more southerly component to the winds. Natural wind slab avalanches are likely today, and human-triggered wind slab avalanches are very likely. Wind slab avalanches could be large and destructive. Some wind slabs could entrain some wet snow in areas where significant rain has fallen.

• 

  Loose Dry

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1

  The heavy snow from this storm has accumulated on top of lighter old snow and may not have had time to bond to this old snow surface. In addition, changes during the storm may create weaknesses within the storm snow that the intense snowfall expected today could quickly overload. Human triggered storm slab avalanches are likely today on steep sheltered slopes above 8000 ft. where more snow has and will continue to accumulate. Below 8000 ft. some storm slabs could also exist on slopes where new snow loads the slopes today. Some storm slabs could entrain some wet snow in areas where significant rain has fallen. In lower elevation areas where rain continues to fall, some loose wet avalanches may remain possible. 

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  3

  Deep slab avalanches also remain possible today. Prior to this storm tests and observations continued to indicate that a weak layer of graupel resting on a melt-freeze crust 2.5 to 5 ft below the surface could still fail. The storm has added a heavy load on top of the existing snowpack and could provide enough weight to trigger this deep slab problem or push it to the edge where the additional weight of a person on a slope could possibly trigger a deep slab. East aspects above 9000 ft. in the Mt. Rose backcountry are the most suspect for deep slab activity, but observations have found this layer in other places along the Sierra Crest as well. Due uncertainty surrounding this problem, deep slabs may be possible on any aspect with an east component (NE-E-SE) above 9000 ft.

  The only effective deep slab management strategy is to avoid areas where a deep slab problem may exist. Avoiding aspects of concern, using slopes under 30 degrees on aspects of concern, and avoiding connected terrain where remote triggering could occur represent avoidance strategies.  Any avalanches associated with this weak layer would be large and have severe consequences.