Sawtooth & Western Smoky Mtns

Avalanche problems

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Likely

  Size

  2

  With 15-20 inches of new snow over the past few days, you can expect to find a range of new snow problems today. These broadly fall into two categories:

  SLABS: Shifting winds have blown from a variety of directions since the new snow fell. You can trigger slabs that fail within this new snow, or a bit deeper on the layer of weak snow that we buried at the start of the month. Read more about this budding persistent slab problem in the Forecast Discussion below. Look for drifts, dunes, and rippled snow surfaces as an indication that the wind has been at work. Cracks shooting out from your skis or machine are a clear sign that you've found an unstable slab that could be triggered on steeper slopes. 

  LOOSE SNOW: In terrain sheltered from the wind, expect small loose snow avalanches to be easy to trigger. If you're hunting cold snow on northerly aspects these sluffs will have a dry character. On slopes where the sun is warming up and melting the snow surface, these loose snow slides will have a wet character. Thin clouds and southerly winds should help to mute some of our wet snow issues today. However, if you're finding moist/wet snow at the surface or if you are seeing wet balls of snow rolling down the slope this type of slide is coming onto the menu. Loose snow slides will start out small, but can pick up steam quickly thanks to the stiff and crusty surfaces underneath the recent snow. 

  Avalanches involving the new snow will range from small to large enough to bury you. Triggered and natural avalanches involving the new snow can be effective triggers for avalanches failing on the deeper weak layer described below. 

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  Under the recent storm snow, you will find thick, very dense slabs resting uncomfortably on layers of weak snow. This combo has produced dozens of recent avalanches in the neighboring Galena Summit and Eastern Mtns zone. Many of these slides have been large enough to snap mature trees and destroy large vehicles. Our limited observations indicate that recent activity has been less widespread in this zone. 

  If you dig down, you'll find thick piles of facets with or without surface hoar on shaded aspects, and crust+facet combinations on slopes that get more sun. Recent avalanche activity has been much more widespread on shady slopes, but a few large avalanches failing on slopes that face the sun indicate that this problem exists in those areas as well. 

  Because the slabs on top of this weak layer are so dense, and the new snow is so soft and fluffy, you aren't likely to encounter many or any signs of instability before triggering a large, potentially unsurvivable avalanche. Keep this weak snow at the front of your mind when you are moving through the mountains. The only guaranteed way to avoid this problem is to steer clear of avalanche terrain and slopes threatened by overhead hazard. Any avalanche that fails on this weak layer will be large and destructive, and slides can be triggered from long distances away (remote triggering).