Soldier & Wood River Valley Mtns

Lawinenprobleme

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  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1–2

  What is it? Yesterday a skier triggered a large avalanche on the north slope of Della Mtn outside of Hailey (report). He was able to keep his speed to get to lower-angled terrain and watched the avalanche go by him onto the valley floor. Today, you can find the same sensitive 1-3 foot thick slabs in many areas with the recent wind-affected snow.

  Where is it?  These slabs will be largest and thickest at upper elevations, but you'll also find wind slabs in exposed lower and middle elevation terrain. The foothills around Fairfield and the steep slopes at the mouths of drainages that feed the Big Wood River are common locations to find these lower elevation slides. Be on the lookout for wind slabs from the valley bottom to the mountain tops and expect them to be easy to trigger. 

  How can you recognize it? Cracks shooting out from your skis or sled and collapsing clearly indicate instability. Look for ripples in the snow, dunes capping ridgelines, and drifts along the sides of gulleys or chutes. Wind-deposited snow will be stiffer and keep your skis or snowmobile on or closer to the surface. Some of these slabs might be masked by recent snow and be more hidden.     

  How can you manage it? Most wind slabs are building on top of persistent weak layers in the snowpack (read Problem #2 below). Because of this, the wind slabs you encounter today may behave more like persistent slabs than "simple" wind slabs. Fresh slabs will be reactive to your weight and may produce avalanches that break wider and deeper than you might expect. Triggering these avalanches remotely (from a distance above, below, or to the sides of steeper slopes) is a real possibility.

  

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  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Likely

  Größe

  1.5–2

  What is it? Layers of weak snow in the upper snowpack can produce 1-3' thick slab avalanches. Expect to find weak, sugary facets on shaded slopes and crust+facet sandwiches on slopes that face the sun. You're most likely to trigger a slide involving these layers in areas where the wind has built a slab on top. 

  Where is it? The depth of these weak layers varies from slope to slope, but it's safe to assume that they exist on most slopes. The sensitivity will be amplified in wind-affected terrain (picture to right/above) in more exposed terrain. It is also possible to trigger slides in more sheltered locations, like in the bottom right of this photo.

  How can you recognize it? Shooting cracks and collapsing are clear signs of an unstable snowpack.Natural and human-triggered avalanches will offer guidance on what type of terrain and slopes these avalanches are likely to be triggered on, but it's safe to assume that they exist on many slopes.  It might take some digging into the snow to reveal previous wind-affected layers that the new snow has masked in more sheltered locations. 

  How can you manage it? Persistent weak layers can fail unpredictably and break significantly wider and deeper than you might expect, producing much larger avalanches. Today I recommend you choose simple, conservative terrain to play in. Pay close attention to the terrain around you and what you are connected to in slope steepness. Pockets of slopes steep enough to slide have proven to be enough to cause avalanches, like the one on Della Mtn. Cliffs, trees, and terrain traps magnify the consequence of even small slides.