Sawtooth & Western Smoky Mtns

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Certain

  Size

  1.5–2

  Avoid all wind-loaded avalanche terrain. Expect to trigger 1-3 ft thick slabs where the wind drifted snow. Natural avalanches are possible. Both the size and likelihood of avalanches will increase as you move up in elevation and as today's storm progresses. You may find wind slabs in middle elevation terrain that is typically sheltered from the wind. In the steep, craggy Sawtooth Mtns, slabs also commonly form on the aprons below cliffs and couloirs.

  Many of the wind slabs overlie well-developed weak layers, resulting in avalanches that could break easily, wider than expected, or above you. 

  If the snow surface becomes stiffer, you've found a wind slab. Cracks shooting out from your skis or boards are an obvious sign of instability. Watch for ripples, dunes, and fresh cornices, signs the wind has been at work. 

  Wind Slab avalanches could "step down", triggering the much larger Persistent Slab avalanches described below. 

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2–3

  Huge, destructive avalanches over 3 feet thick are likely in wind-loaded terrain and possible in sheltered areas. Snowfall and wind-driven snow is overloading weak faceted snow near the ground. The likelihood of triggering one of these slides will increase throughout the day as the storm progresses.

  You may or may not observe obvious warning signs like snowpack cracking or collapsing before triggering a slide. Avalanches could be triggered remotely, from gentler terrain below, above, or to the sides of steep slopes.  Persistent Slab avalanches can break wider and higher on slopes (above you!) than you might expect.