Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger is highest in the eastern portion of this zone—the Little Wood Drainage, Mormon Hill, and Swede Peak areas—where significantly more snow fell. Here, avalanches are possible even on sheltered slopes. Across the zone, look for signs of recent wind drifting such as dune-like drifts and ripples on the snow surface. Cracks shooting from your skis or board are signs that you've found a sensitive slab.  Bright sunshine between periods of clouds will melt the snow surface and increase the hazard of loose snow avalanches. Pay attention to the snow surface as the day progresses. If it is getting wet, be alert to the increasing likelihood of these slides, particularly in very steep, rocky terrain. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Storm totals vary greatly across this zone. In the Soldier Mountains, on the western side of this zone, 2-4 inches of snow were recorded. The eastern side of this zone—in the Little Wood Drainage and near Mormon Hill—12-16 inches of snow fell. Because of this, avalanche danger is significantly higher on the eastern side than the western side. Across the zone, moderate winds blowing from a variety of directions built wind slabs out of the new snow in exposed, upper elevation terrain. The new snow (and the fresh slabs) were deposited on a variety of surfaces that formed during last week's clear weather. The wind slabs you encounter today are most likely to be reactive where they were deposited on weak, faceted snow. This slab+weak layer combination is most likely on slopes on the northern half of the compass, particularly on the eastern and western margins, where these facets are accompanied by a fragile crust.  Look for evidence of wind drifting such as dune-like drifts and ripples on the snow surface. Cracks shooting out from your skis or board are a sure sign that you've found a sensitive wind drift. 

    ADDITIONAL DISCUSSIONSnowfall this weekend heavily favored the eastern portion of this zone. In these areas, over a foot of dense snow fell on a thin and very weak snowpack. Unsurprisingly, the snowpack did not react well to this rapid loading. Yesterday, as I traveled just north of this zone in the East Fork of the Big Wood drainage, I looked south and spotted large avalanches on many slopes (pictured at right). These slides were breaking hundreds of feet wide, failing at the interface between the new snow and the old snow on slopes that faced away from the sun. In these areas, the long dry spell had significantly weakened the snowpack, leaving a stack of poorly consolidated, faceted snow. These types of slides fail in surprising ways and are possible even in areas sheltered from the wind. They may be triggered remotely, from a distance above, below, or to the side of avalanche starting zones. Build in a wide safety margin if you are traveling in areas where more snow has fallen. 

Avalanche Discussion

Let's think about spatial variability this morning. The storm this weekend and the avalanche activity that followed provides a great lens to look at the way things change over a distance:

  1. For the better part of the season, snowfall has heavily favored our northern zones. If you live and ski in the Wood River Valley, I don't have to remind you of this. That pattern was flipped this weekend, when a stream of moisture out of the south impacted our area, a pattern that we haven't seen since Christmas. The Sweede Peak SNOTEL recorded 15" of snow and 1.3" of SWE while Banner Summit and the Sawtooths picked up just a few inches of snow. 
  2. In the mountains above the Wood River Valley and the Little Wood drainage, the character of the snowpack is primarily a function of aspect. On slopes that face the sun, the snow has been slowly melting away over the past months, leaving nothing but dirt and sagebrush. On shaded slopes, the little snow on the ground has faceted significantly, resulting in a very thin and weak snowpack. Don't believe me? Drive north from Hailey to Ketchum and make a note of how much bare ground you see (lots). Then, turn around and drive back south and look at how much more snow-covered ground you can see.

Now, try to overlay these two patterns in your head. The areas where the most snow fell and the snowpack was weak are the areas where I observed large avalanches yesterday (photo). Keep these patterns in mind as the weather continues to bring snow to our southern mountains in the coming days and weeks. Unfortunately, this type of avalanche problem won't go away quickly. 

Regions covered