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

  1.5–2.5

  A number of weak layers exist in the upper 1-4' of the snowpack:

  • A batch of surface hoar was buried 10 days ago (video from Copper Mtn). It is now buried 1-2' beneath the snow surface. In places you'll also find facets with or without a crust here. The slab overlying this weak snow has been a bit too soft and too thin to produce widespread avalanche activity, but the multiple human-triggered slides on this layer in the past week prove that it is capable of producing slides (photo at right/above, information on Galena Summit avalanches here). New snow overnight has added mass to the overlying slab, making it easier to trigger a slide on this layer. 
  • Weak snow buried in December now sits 2-3' beneath the snow surface. In this zone you'll find weak facets, facets on a crust, and occasional surface hoar at this interface. This layer is now capped with a meaty slab, which makes it harder to impact with your weight. 

  You are much more likely to trigger a slide involving weak snow that is closer to the surface. It's easier to impact this snow with our weight. Enough snow has fallen that these slides may be large enough to bury you and can certainly knock you off your feet and push you through ugly terrain. Deeper weak layers are harder to impact with your weight, but the resulting slides will be larger and much more destructive.

  It's a safe bet that most slopes have at least one of these weak layers. You're most likely to trigger avalanches on slopes where the wind has formed drifts or slabs or stiffened the snow at the surface (example), but these slides are also possible in sheltered terrain. Pay close attention to the snow: cracking and collapsing are obvious signs of instability. But, don't expect to get direct feedback. The first sign of instability may be the avalanche that you trigger.

  Persistent slab avalanches behave in ways that catch experienced backcountry travelers off guard. They can break wider than you might expect, and can be triggered from long distances away from steeper slopes. 

  ADDITIONAL DISCUSSION: While triggering slides on faceted snow near the base of the snowpack is unlikely, it can't be ruled out in steep, rocky, wind-affected alpine terrain. Slopes like these have variable snow depths, and thinner snowpack areas allow our weight to more easily impact deeply buried weak layers.

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

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

  Probabilidad

  Likely

  Tamaño

  1–1.5

  2-5" of snow fell here overnight. Winds blew at moderate to strong speeds out of the southern portion of the compass. Expect to find a fresh batch of relatively small wind slabs in exposed terrain today. Look for these slabs near ridgelines and in mid-slope features like gullies. Places like this slow the wind down and force it to drop whatever snow it is carrying, building slabs in the process. 

  Pay attention to how deep and how dense the snow you are traveling in is. If the snow depth and density increase as you head into exposed terrain, you are likely traveling through a fresh wind slab. Cracks shooting out from your skis or machine are clear indicators that you've found an unstable slab. These slabs are adding stress to the weak layers described above. Triggered wind slabs can step down to these weak layers, creating a larger, more dangerous avalanche.