Central Sierra Nevada

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1.5–2.5

  More snow and strong winds keep adding layers of wind-blown snow on top of existing wind slabs. Wind slab avalanches have occurred every day of this storm and remain likely on slopes near ridges, open faces, and gullies today. NW-N-NE-E-SE aspects near and above treeline hold the largest and most reactive wind slabs. A few wind slabs may also lurk in below treeline areas or on other aspects due to the strength of the winds. Large, fragile cornices that can fail far from their edges loom over many slopes.

  Recent observations have shown inconsistent wind slab strength with fragile easy-to-trigger wind slabs adjacent to more stubborn wind slabs. Cornices above a slope, blowing snow, and wind-created surface textures can help identify wind-loaded slopes. Recent avalanches and snow cracking represent signs that wind slabs remain unstable. Giving wind-loaded areas a wide berth makes sense today, especially since dense wind slabs could break above a person or after someone gets onto a wind-loaded slope.

  

• 

  Storm Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Changing conditions during the storm have left weaknesses in the storm snow, including layers of heavier storm snow on top of lighter layers, graupel layers, and crusts. So far, signs of storm slab instability have remained limited. Still, the possibility of a storm slab avalanche exists on steep slopes, even in below treeline areas and other typically sheltered areas. Storm slabs often occur near convex rollovers on a slope. 

  Look for cracking in the storm snow and feel for different layers of snow as you travel to help identify where unstable storm snow might exist. If you see any signs of storm snow weakness or doubt a slope's stability, bypass that area for somewhere without signs of instability. 

  

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  Wet snow exists on slopes below ~7500 ft. Wet loose avalanches remain possible on steep slopes, especially where rain keeps falling on snow. Some of these may remain small due to the limited terrain at lower elevations, but some may entrain enough snow to cause problems for people.

  Watch for signs of unstable wet snow like rollerballs, pinwheels, and shin-deep wet snow. If signs of wet snow instability exist, move to less steep terrain.