Sawtooth & Western Smoky Mtns

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  1–2

  Expect to encounter freshly formed, sensitive wind slabs in terrain exposed to the wind. Some of these slabs are building atop crusts and facets. In these areas, slabs may be particularly sensitive and break wider than expected. Look for smooth pillows, dunes, waves, and textured surfaces of windblown snow near ridgelines, mid-slope gullies, and in cirques below large cliff bands. You may find wind slabs on open slopes at middle elevations as well, given the strength of the winds associated with the current storm. Cracks shooting from your skis or sled are a clear sign that you've found an unstable slab. These smaller avalanches can serve as an effective trigger for the much larger and more dangerous persistent slab problem described below. 

  ADDITIONAL DISCUSSION: Loose snow avalanches are possible during periods of intense snowfall. These could run faster and further than expected given the smooth, crusty surfaces present on many slopes before this storm.

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  2

  Although unlikely, you could trigger a 2-3 ft thick persistent slab avalanche on buried weak layers (sugary facets, surface hoar, and crust + facet combinations). This problem is worst on middle and upper elevation slopes facing NW-N-NE-E. 

  Unfortunately, unstable slopes probably won't provide obvious signs of instability, like snowpack cracking or collapsing. Snowpack stability tests are likely to be inconclusive and are of limited use. Tracks on a slope don't mean it's safe. Avalanches can be triggered by the second, third, or fourth rider on a slope. In low probability/high consequence situations like this, there's a good chance the first sign of instability you'll see is the avalanche you trigger.

  The likelihood of triggering a slide is decreasing, but the thick, dense slab makes the consequences severe. Persistent weak layers can fail unpredictably and break wider and higher on slopes than you might expect. Avoiding avalanche terrain is the only surefire way to manage this problem. Short of that, you can reduce your risk by avoiding large avalanche paths and those with ugly consequences if you are caught in a slide.