Soldier & Wood River Valley Mtns

Lawinenprobleme

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Hochgebirge
  • Waldgrenze
  • Unterhalb der Waldgrenze

  Wahrscheinlichkeit

  Possible

  Größe

  2

  What and where is it?

  • The slabs: February storms formed 1-3 foot thick slabs on many slopes. The slabs are largest, stiffer, and most widespread in wind-loaded middle and upper elevation terrain.  However, last week's strong wind built slabs on more middle and lower elevation slopes than usual.
  • The weak layers: The slabs overlie multiple weak layers (sugary facets, surface hoar, or crust + facet combinations) on many slopes, including sunnier aspects. The weak layers remain most suspect on slopes facing the northern half of the compass (NW-N-NE-E). 

  This diagram shows the spatial pattern of recent avalanche activity. Many recent avalanches were hundreds of feet wide, pulled into gentle terrain, and / or were remotely triggered.  

  How can we recognize and manage this problem?  Determining whether a given slope is safe to shred or waiting for a trigger—you— is challenging. Due to the variable distribution and character of both the slabs and weak layers, stability can change quickly over short distances. You may or may not observe snowpack cracking and collapsing, clear signs of unstable conditions, before triggering a slide. 

  Unfortunately, the only surefire way to avoid trouble is to give avalanche terrain a wide berth. You can stack the odds in your favor by steering clear of steep, wind-loaded slopes, especially those facing away from the afternoon sun (NW-N-NE-E aspects). Watch for dunes, waves, and textured surfaces created by wind. Wind-driven snow and slabs feel stiff. Recognize that you could trigger avalanches on slopes above, below, and to the sides of where you are riding or skiing. 

  Additional Discussion - New Snow issues: The fresh snowfall and wind-drifted snow may not bond well to the old snow surface. You may see small loose snow slides (sluffs) or thin wind slabs where more than a few inches of new snow falls. If you're traveling in upper elevation terrain, be alert for fresh instabilities involving the new snow. While these slides will be small, they could trigger the larger, far more dangerous Persistent Slab avalanches described above.