Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Winds shifted to the NE and increased enough to start moving snow through the night. Expect to find new slabs of wind drifted snow on slopes loaded by these NE winds (SE-S-SW-W-NW aspects). These new wind slabs will continue to grow today as the NE winds continue transporting snow. While these NE winds will scour many of the previously wind-loaded N-NE-E aspects, they may also stiffen some of the old wind slabs on those slopes. Wind slabs could exist on almost any aspect near ridgelines, in gullies, and on open slopes near and above treeline due to a combination of new wind slabs and lingering old wind slabs. Human-triggered wind slab avalanches large enough to bury or injure a person (size D2) will be possible today. The strong March sun could also make triggering some of these wind slabs easier today. 

  Cornices above a slope, pillows of wind drifted snow, ripples on the snow surface, and other wind-created textures can help identify where wind slabs exist. Identify where fragile wind slabs may exist and build travel plans with appropriate safety margins. These could include avoiding wind-exposed terrain in favor of more sheltered terrain where softer snow exists or traveling on lower angle slopes. 

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  The strong March sun should provide enough warming to introduce the possibility of wet loose avalanches today. Lower elevation sun-exposed slopes will experience the most warming since cooler temperatures and strong NE winds should help keep some of the higher elevations colder. Wet loose avalanches could entrain much of the recent snow and could get large enough to cause problems for people if they occur in terrain with long steep slopes. It is not impossible for some of the wet snow avalanches to have slab characteristics. On aspects where the snow remains cold, sluffs of unconsolidated snow may also remain possible on steep slopes today. Terrain traps like cliffs, trees, rocks, etc could magnify the consequences of any size avalanche.

  Rollerballs, pinwheels, and wet sticky snow all indicate rapid warming in the snowpack. As soon as you see signs of wet snow forming it is a good time to start looking for colder snow on more shaded aspects or moving into lower angle terrain.