Central Sierra Nevada

Lawinenprobleme

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  1–2

  Shallow wind slab avalanches were triggered yesterday. New, potentially larger wind slabs will form today as increasing SW winds drift and deposit snow into lee areas. These new wind slabs will form mainly above treeline and near treeline on NW-N-NE-E-SE aspects.

  Look for areas of blowing and drifting snow and identify where it is depositing as a wind slab. Move around these areas with caution. Account for downslope hazards such as cliffs and terrain traps that could magnify the consequences of even a small avalanche.

  

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  Deep Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  2–3

  Deeply buried weak layers are still an issue in the snowpack. A large (D2) avalanche that failed very deep in the snowpack was remotely triggered yesterday on a NE aspect somewhere on the northerly side of Mount Rose proper (not the ski area). A large collapse and unstable snowpit tests on the Dec 11 layer were also reported yesterday from Trimmer Peak below treeline on a NNW aspect (Luther Pass area) giving further indication of this problem in places where the snowpack was shallow prior to the last storm cycle. A recent persistent slab avalanche likely less than 24 hours old was seen yesterday on The Nipple (Carson Pass area).

  This is a very difficult avalanche problem to manage as snowpack stability will seem fine right up until the moment it is not. Most people will get lucky traveling suspect terrain without incident. Maybe you can get clues to an unstable slope from triggering an isolated collapse (likely with an audible whumpf sound) or by digging really deep to find unstable snowpit test results. Short of either of those, triggering a large avalanche will likely be the first feedback that terrain selection choices were not the right match for the current conditions.

  Scale back terrain choices if you are traveling in an area with recent reported avalanche activity or anywhere the snowpack was still shallow prior to this last storm cycle such as anywhere along the Carson Range on the NE, E, and SE sides of Lake Tahoe and locations east of the Sierra Crest in the Luther Pass, Carson Pass, and Ebbetts Pass areas. The easy way to avoid this avalanche problem is by either avoiding NW-N-NE aspects and recreating on any of the other aspects or by utilizing only sub 30 degree angle slopes on NW-N-NE aspects without steeper terrain above or to the side.