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Problèmes avalancheux

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Possible

  Taille

  1–1.5

  Recent snow and strong SW-W winds are likely to have built thin drifts and slabs at upper elevations. Look for this problem near and just below exposed ridgelines and along cross-loaded mid-slope gullies. Recent cornice growth, pillows, and dunes are all clues that wind was at work moving snow.  Cracking and collapsing are sure indications that you've found a sensitive slab. You can reduce your odds of triggering a wind slab by sticking to more wind-sheltered slopes with soft powder at the surface.

   

  

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpin
  • Limite forestière
  • Sous la limite forestière

  Probabilité

  Unlikely

  Taille

  2

  Although unlikely, you could trigger a 2-3 ft thick persistent slab avalanche on buried weak layers (sugary facets, surface hoar, and crust + facet combinations). This problem is worst on middle and upper elevation slopes facing NW-N-NE-E. 

  While the odds are low, the consequences of triggering one of these dense, thick slabs are severe. Don't expect obvious signs of instability. In low probability/high consequence situations like this, there's a good chance the first sign of instability you'll see is the avalanche you trigger. Tracks on a slope don't mean it's safe. Avalanches can be triggered by the second, third, or fourth rider on a slope. 

  Persistent slabs can fail unpredictably and break wider and higher on slopes than you might expect. Avoiding avalanche terrain is the only surefire way to manage this problem. Short of that, you can reduce your risk by avoiding large avalanche paths and those with ugly consequences if you are caught in a slide.