Soldier & Wood River Valley Mtns

Avalanche problems

• 

  Persistent Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  2–3

  As we move away from the loading event that brought improved skiing and riding conditions to our area, we focus our attention on the persistent weak layers that are buried in the snowpack. There are three broad categories:

  1. Last week's storm buried a variable snow surface. In most portions of this zone, the storm didn't bring enough snow to build much of a slab on top of these layers yet. In areas where the wind has built slabs, these layers may make those wind slabs easier to trigger (Problem 2 below).
  2. Weak layers that formed at the end of January and during the month of February are now buried 1-3' deep. These layers have produced avalanches across most of our forecast area in the past two weeks (Dollarhide, Galena Summit, Smiley Creek, Beaver Creek, Sawtooths, Banner Summit). The pattern of activity outlined by these avalanches points to these layers being most unstable on slopes that face the sun, where they are accompanied by crusts. The photo at right/above shows a few of these layers
  3. A layer of large-grained weak snow (depth hoar) exists near the ground in this zone. Triggering a slide on this snow is a low probablility/high consequence type of problem. You are more likely to trigger slides on the weak layers higher up in the snowpack, but any slide triggered on this deeply buried weak snow is likely to be unsurvivable.

  As their name implies, persistent weak layers tend to stick around for quite a long time. As days pass without loading, the snowpack is getting some time to rest, which will gradually decrease the likelihood of triggering an avalanche on these weak layers. However, the possibility of triggering a slide here will be on the table for some time to come. If you choose to enter avalanche terrain, be alert that at least one of these weak layers almost certainly exists in the snowpack underneath you. Even as the danger decreases we still advise cautious and conservative terrain selection. Be alert to the consequence of being caught in a large avalanche in the terrain you are recreating in.

  

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Possible

  Size

  1–2

  The combination of new snow and wind has built slabs in terrain where the wind blows. Much more snow fell in the western portion of this zone (Dollarhide and west into the Soldiers) and the slabs will be larger and more reactive here. On Saturday, Soldier Mountain Cat Ski guides triggered several wind slab avalanches with explosives. Some of these slabs were small, but one was large enough to bury or injure a person. These wind slabs are becoming less sensitive to the weight of a skier or rider, but some are sitting atop weak snow surfaces (facets and/or crusts) and remain touchy.  Recognize that wind-loading also adds stress to the weak layers buried in the snowpack (described in Problem 1 above). Any wind slab you trigger could step down to these deeper layers, producing a much larger, more dangerous avalanche.