Soldier & Wood River Valley Mtns

Problemas de aludes

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Possible

  Tamaño

  2–3

  Skiers triggered avalanches involving layers of weak snow on each of the last three days (Avalanche Database here). All were large enough to bury you, or worse. A remotely triggered slide yesterday put 4' of debris on a summer trail nearly 2,000' below where it started. Stop, take a look at the photo to the right/above, and read that again. 

  These layers of weak snow have proven to be most widespread on slopes that directly face the sun. Here, you'll find a crust with weak facets sitting on top of it, all capped by a dense slab. On slopes that face away from the sun, the distribution of these weak layers is spottier. Some slopes harbor pockets of surface hoar and small facets that is reactive in snowpack tests and others don't. 

  Triggering an avalanche involving these layers remains a very real possibility today. Recent winds are building slabs and adding stress to these weak layers. You're most likely to trigger one of these slabs in steep terrain that has been recently wind-loaded, but this problem exists in sheltered terrain as well. Avalanches on persistent weak layers can be triggered from long distances away from steeper slopes. They can break wider than you might expect, pull back into gentler terrain above steeper slopes, and impact valley bottoms. 

  Want to significantly decrease your risk of triggering a large avalanche today? You can do so by sticking to gentler terrain, free of overhead hazards, that is sheltered from the effects of the wind. As a bonus, you'll also find the best skiing and riding here.

  ADDITIONAL DISCUSSION - WEAK SNOW NEAR THE GROUND: A layer of weak, faceted snow exists near the base of the snowpack. This layer has produced hundreds of avalanches this season. I triggered the most recent avalanche involving this weak snow on Friday in the Baker Creek drainage. This weak snow is buried beneath a thick, very dense slab of snow. Impacting deeply buried weak layers with your weight isn't easy, but the consequences are grave. You're most likely to trigger this layer in steep, wind-affected alpine terrain where snowpack depths are variable. Here, you'll have better access to this weak snow. Digging down to this weak snow with the track of your sled is another "great" way to impact this deep weak layer.

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque

  Probabilidad

  Likely

  Tamaño

  1–2

  Human-triggered wind slab avalanches occurred in this zone on each of the past two days. On Saturday, an experienced skier was caught and carried in a slide on Senate Peak. Yesterday I triggered a wind slab that produced a large debris pile on Galena Peak (photo at right/above). Slab growth continued overnight, and wind slabs will be reactive to your weight today. 

  While you are most likely to find large, sensitive wind slabs at upper elevations, that isn't the only place they exist. Moderate to strong gusty winds build slabs down into middle elevation terrain as well. Winds blowing from unusual directions (NE-E-E) build slabs in places you don't normally find them. I can hear the wind blowing outside the office here in Ketchum, and I'm sure there are some slabs building in the low elevation terrain in this zone. Be on the lookout for signs the wind has been moving the snow around, like drifts and dunes and scalloped textures on the snow surface. If you're traveling through thick, dense snow and seeing cracks around your feet, skis, or machine, you've found a sensitive wind slab. Even small avalanche terrain can have severe consequences where there are terrain traps like creek beds, and fast transitions from steep slopes to flat terrain below.

  Be on the lookout for signs the wind has been moving the snow around, like drifts and dunes and scalloped textures on the snow surface. If you're traveling through thick, dense snow and seeing cracks around your feet, skis, or machine, you've found a sensitive wind slab. Even small avalanche terrain can have severe consequences where there are terrain traps like creek beds, and fast transitions from steep slopes to flat terrain below. These slabs are adding stress to the weak layers in our snowpack, described above. Any triggered wind slab has the distinct possibility to step-down to the deeper weak layers described above. The result will be a much larger and more destructive avalanche.