Sawtooth & Western Smoky Mtns

Lawinenprobleme

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  2–3

  You're most likely to trigger a persistent slab avalanche on steep slopes that tilt away from the afternoon sun (NW-N-NE-E). It's these aspects that produced the most widespread natural and human-triggered avalanches over the last two weeks, and where our buried weak layers remain the most concerning. 

  Triggered avalanches may be 2-5' thick and release in surprising ways. They can be much wider than expected and be triggered remotely—from flat terrain below, above, and to the sides of steep slopes.  

  Snowpack cracking and collapsing are clear signs of unstable conditions. The best way to avoid trouble is to give avalanche terrain a wide berth. This includes gentler terrain below steep slopes. 

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  2

  Up to 2 feet of snow and strong winds built 2-4' thick drifts and slabs at upper elevations. Expect these drifts to be the largest and most sensitive on slopes facing N-NE-E and SE. 

  Look for them near or below ridgelines, along mid-slope ribs, and on aprons beneath chutes. In the craggy Sawtooth Mtns, you may find slabs where snow has "spindrifted" below large cliff faces and couloirs; these areas are also likely to harbor weak snow beneath the slabs. Obvious, recent, cornice growth, dunes, or drifts are all signs that the wind has been at work. If you suddenly feel the snow surface getting stiffer, you've found a wind slab. 

  This problem is formidable on its own, but may also serve to trigger the larger and more dangerous persistent slab avalanches described above.