Soldier & Wood River Valley Mtns

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  2–3

  We have a layer of very weak snow (facets and crusts) buried in our snowpack. In this zone, it sits beneath a 3-4+' thick slab of dense snow that fell in the past 2 weeks. This weak layer has produced numerous large and very large avalanches already this season, including this slide on Galena Peak that was observed in a period of clear weather on Christmas Eve. Other large avalanches occurred in the Smokys (photo, photo) and Sawtooths (photo, photo). I went to check in on this weak snow in this zone on Saturday (video at right/above) and was not encouraged by what I found. 

  Weak layers like this are hard to deal with. They behave in ways that tend to catch even very experienced backcountry travelers off guard. Avalanches can be triggered remotely, from long distances below, above, or to the sides of steeper slopes. Avalanches that fail on this snow may pull back into gentler terrain above steep slopes thanks to the very dense slab of snow. Any avalanche that breaks on this weak snow will be very large, and likely unsurvivable. We are in the middle of an ongoing loading event and the weak snow is struggling to support the added load. It won't take much to push it to its breaking point: that could be a collapsing cornice, a natural wind slab, a few extra snowflakes, or you. 

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Very Likely

  Size

  1–2

  This week's storm delivered snow totals measured in feet and a healthy dose of wind to go along with it. Moderate to strong winds blowing out of the S-SW yesterday and are in the process of shifting to blowing out of the W-NW today. As the wind shifts, freshly drifted snow will mask the presence of older, larger drifts underneath. Be on the lookout for these multiple generations of slabs and know that you will be likely to trigger one when you find it. A sudden increase in snow depth and snow density are great signs that you are traveling through a wind slab. Slabs will be 1-3' thick and easily large enough to bury you. These slabs are hazardous in their own right and are also adding weight to the persistent slab problem described above. If you find yourself traveling in an area where both of these problems exist I would strongly recommend that you rethink your choice of terrain.

  In the mountains above the Wood River Valley we often see small avalanche cycles related to shifting winds during the passage of cold fronts. There is plenty of snow available for transport right now and we will see a front pass through the area this morning. If these winds blow for a few hours I wouldn't be surprised to see small natural wind slabs failing at all elevations, particularly near the mouths of major drainages.