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

  2–3

  Wind slabs formed on leeward facing NW-N-NE-E-SE aspects during the storm. Triggering a wind slab avalanche will remain possible today, especially on slopes below cornices, in gullies, and on open slopes where wind-drifted snow has piled up. Most of this terrain exists in near and above treeline areas, but a few wind slabs may exist in wind-exposed areas below treeline. The light NE winds overnight may have made some of these wind slabs more cohesive. In areas where the wind slabs rest on top of old weak layers mentioned below, more destructive avalanches with wider propagation could occur.

  Cornices above a slope, snow drifts, and wind-created surface textures can provide clues about where wind slabs may exist, and recent avalanches or cracking in wind-blown snow represent sure signs that those wind slabs remain unstable. If you venture into exposed areas today, gather as much information as possible from small slopes without consequences before even considering larger terrain. Still, unstable wind slabs that fail on the weak layers mentioned below could surprise you by avalanching on a slope with no other signs of instability. 

  

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  2–3

  Multiple layers of concern ranging from crusts and weak snow at the base of the storm snow to old graupel layers to buried surface hoar exist in the snowpack. Triggering an avalanche remains possible on these layers, especially on NW-N-NE aspects. If one of these layers does break, 2 to 4+ft deep avalanches could occur.  Any steep slopes where these layers exist remain suspect today especially slopes with trigger points like convex rollovers.

  Correctly identifying which slopes may avalanche or which weak layers may fail is difficult. These kinds of avalanches catch people by surprise on slopes they thought seemed stable. Trying to outsmart this problem often results in triggering an avalanche that breaks wider than expected and has serious consequences. Patience and avoidance represent the best tools for dealing with persistent slabs. Give them time, and enjoy the soft winter-like snow on lower-angle slopes not connected to avalanche terrain.