Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Human-triggered avalanches failing on layers of weak snow are possible. These are much more likely in wind-affected terrain, but are possible in sheltered terrain as well. Yesterday's storm built thin, relatively small wind drifts and slabs that may be reactive to your weight today. The consequences of being caught in even small slides can be high in terrain with rocks, cliffs, trees, and terrain traps. You can reduce your risk today by steering clear of recently wind loaded slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Several weak layers exist in the upper few feet of the snowpack. A prominent layer of surface hoar buried 1-1.5 feet deep has been responsible for a handful of skier and rider-triggered avalanches in the past few weeks. The most recent slide occurred near Galena Summit on Sunday (report here, photo at right/above). This layer is at its worst on sheltered, shady (W-N-E) slopes. Above this, you'll find a few layers of crusts, facets, and/or surface hoar that were buried in the second half of January. Yesterday's storm added some weight on top of these weak layers and triggering a large avalanche involving them remains possible. In most places you'll need some added load or stiffening from the wind in order to produce avalanches on this layer.

    Older weak layers continue to be worrisome in this zone. Crusts, facets, and/or surface hoar are buried beneath dense, 2-4 foot thick slabs. These hefty slabs make it more difficult to impact these deeper weak layers. You'd be most likely to trigger a slide involving older weak layers in rocky, wind-affected, alpine terrain. Slopes like these have variable snow depths, with thinner areas of the snowpack that make it easier to impact these weak layers. 

    Slides that fail on persistent weak layers are less predictable than simple wind slabs. They may break wider than you expect and may wrap around terrain features that confine wind slabs. Persistent slabs can break well above you on the slope you are skiing or riding on.  Triggered wind slabs can "step-down" to these deeper weak layers, resulting in larger, more destructive avalanches.

    (1/30/2023) This 1-2 foot thick, skier-triggered avalanche failed on a layer of buried surface hoar. Surface hoar is frequently found in shady, partially treed locations like this. N-NE aspect near 9100' in the Salmon River drainage near Galena Summit.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Yesterday's storm brought 2-6" of new snow and a healthy dose of wind to this zone. Wind direction shifted through the storm, building wind slabs on many exposed slopes.  Wind loading and slab growth will continue this morning until wind speeds ease off later in the day. Be on the lookout for fresh slabs near ridgelines and on the sides of mid-slope features like gullies and ribs. Extreme winds have been blowing in the Soldiers have likely built stiff, hard slabs at all elevations.

    Though small, these fresh slabs will be sensitive to your weight today. They are sitting on a variety of weak snow surfaces developed in the time since our last snowfall. As you travel through the mountains, look for signs that the wind has been at work. Dunes, pillows, and ripples on the snow surface indicate that the wind has been transporting snow. If the snow you are moving through is becoming deeper and denser, you're likely moving through wind-deposited snow. Cracks shooting out from your skis or machine are a clear sign of an unstable slab.

    (1/30/2023) This large avalanche in the N Fork Soldier Ck drainage released on a SE aspect near 9000', likely over the Jan 28-29 weekend.

Avalanche Discussion

In the past month, we've seen the character of the snowpacks in our region diverge. Snowfall in January favored our northern and western mountains. The eastern half of this zone (mountains above the Wood River Valley) was largely missed by these storms. Because of that, the snowpack has remained thinner here and most of the snowpack has faceted. Without a slab overlying the weak snow, triggering an avalanche is unlikely. Further west (from Dollarhide to the Soldiers), ongoing snowfall in January helped to build a slab on top of the weak layers in the upper 1-2 feet of the snowpack.

On sheltered slopes that face away from the sun, you'll find a layer of surface hoar buried about 1.5 feet deep. This layer produced a handful of human-triggered avalanches in January. On slopes that face the sun, you'll find a few sets of crusts with associated facets that were buried in January.  At the surface of the snowpack, you'll find yesterday's 2-6" of storm snow. In exposed terrain, the wind has transported this snow into small slabs that are likely to be reactive to your weight today. Look for them near ridgelines and in mid-slope terrain features like gullies and ribs. Extreme winds have been blowing in the Soldiers have likely built stiff, hard slabs at all elevations. Slides involving the new snow will start small but will pick up speed and snow quickly as they travel downslope, thanks to the stiff crusts the new snow is sitting on.

Go into the mountains today ready to deal with a range of avalanche problems. Spend a bit of time thinking about the consequences of triggering and being caught in an avalanche in the terrain you are in. Even small slides can have bad outcomes on slopes with cliffs, trees, and terrain traps. 

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