Sawtooth & Western Smoky Mtns

Problemi valanghivi

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Likely

  Dimensione

  1.5–3

  You're likely to trigger large avalanches on many slopes. These slides will break widely on a weak snow interface, including slick facets, crusts + facets, and surface hoar, buried and preserved by Monday's storm. Today's heavy snowfall and strong wind will double the thickness of these slabs by sundown, creating dangerous avalanche conditions on all aspects and elevations, including areas that are sheltered from the wind. 

  Anticipate touchy conditions that will only worsen late in the day and as you climb into windier terrain. Persistent Slab avalanches can release in surprising ways. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. Snowpack cracking and collapsing are obvious clues that the slab + weak layer combination you've encountered is unstable. 

  ADDITIONAL DISCUSSION: The shallower Persistent Slabs described above have the potential to step down to release a very large, destructive 4+ foot thick avalanche. These slides would fail on persistent weak layers in the middle or base of the snowpack. The chance we see these beasts will only increase as the storm intensifies this evening and tomorrow.  

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Very Likely

  Dimensione

  1–2

  Today's 5-12" of snow and strong S and SW wind will build fresh, sensitive wind slabs in exposed terrain. Given the intensity of the wind, anticipate these slabs on any open slope, including the mouths of main drainages and roadways that typically funnel wind. In the craggy Sawtooth Mtns, watch for stiff pillows of snow at the bottom of large cliff faces, chutes, and couloirs.

  While dangerous on their own, these fresh slabs are likely to release on the persistent weak layers described above. Cornices will grow rapidly, calving off to release slabs on the slopes below. Drifts, dunes, rippled snow surfaces, and chalky snow pillows are clues that the wind has been at work. If you're experiencing whiteout conditions, you're traveling through the most dangerous overlap of today's avalanche problems.