Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Avalanche danger

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

Triggering a large avalanche remains a possibility—primarily in wind-affected terrain. In these areas, a dense slab may exist atop a variety of buried weak layers. To reduce your risk, avoid slopes with evidence of wind such as fresh drifts or a stiffer snow surface that supports your skis or sled.

Avalanche problems

  • Persistent Slabs

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

    Several persistent weak layers exist in the snowpack. On the plus side, the lack of significant recent loading is allowing these to improve. But on the negative, the variability and complexity of the snowpack make conditions less predictable.

    • A layer of surface hoar is buried 1-1.5' deep on many shady (E-N-W) slopes. While this layer seems to be less common in this zone—especially in the mountains around Ketchum and Hailey—it was likely responsible for at least one triggered slide last week in the Soldiers (photo above/right, details). The surface hoar is most problematic where recent or past wind loading had created a stiffer slab in the upper snowpack.
    • Older weak layers consisting of crusts and/or facets exist deeper in the snowpack. These are buried beneath dense, 2-4+ thick slabs—making them difficult to trigger but capable of producing very dangerous avalanches. While triggering them is unlikely, it can't be ruled out in rocky, wind-affected alpine terrain. Slopes like these have variable snow depths, with thinner areas of the snowpack that allow us to impact deeper weak layers. 

    While there are nuances with each of these, there are common themes. You are more likely to trigger an avalanche on very steep slopes (greater than about 35 degrees) where the wind has influenced the snowpack. You can recognize wind-affected areas by stiffer snow that is more supportive of your skis or machine and surface texture such as ripples, waves, or dunes.

    (1/17/2023) Rider-triggered slab avalanche near Wells Summit. The slide broke ~1' deep on a W aspect at 7,800'. Photo: D. Bassett

  • Wind Slabs

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

    N-NW winds picked up again yesterday afternoon and continued through the night. These sorts of winds are often under-reported by our stations, so it's difficult to predict the extent of new wind loading. Most observers yesterday reported more wind-affected surfaces than wind slabs, but keep your eyes peeled for fresh drifts today. These will be most common in the Soldier Mountains. The lack of loose snow available for transport means wind slabs are likely to be small, but they may be able to knock you off your feet and send you downslope if they catch you unaware. Pay attention to the snow you are traveling through, if it is becoming denser or deeper you are probably moving through a wind slab. Cracks shooting out from your skis or machine are clear indicators you've found an unstable slab.

    (1/22/2023) Wind transporting snow at sunset in the mountains above Smiley Creek.

Avalanche Discussion

We have variable and divergent conditions across our region. This is making our jobs as forecasters difficult, and if you recreate in multiple portions of our forecast area, it means more for you to keep track of too. Here's a (somewhat) brief rundown of how things vary across the forecast area, from north to south:

In the Sawtooths & W Smokys and Banner Summit zones, the primary player is a layer of surface hoar that was buried in early January. The majority of the recent persistent slab avalanches have occurred in these areas. These zones have also received the most recent snowfall, and the layer can be found beneath a stout 1.5-2' thick slab on slopes that face E-N-W. You may be as likely to trigger an avalanche on sheltered slopes as you are in wind-affected terrain. While triggering an avalanche on older, more deeply buried weak layers can't be ruled out in these zones, the more uniformly deep snowpack makes it difficult for our weight to reach these layers.

The Galena Summit & E Mtns zone has a variable and complex snowpack. The early January surface hoar can be found buried 1-1.5' deep, and it produced a few avalanches early on after it was buried. However, it didn't get quite enough load to be a widespread issue, and the surface faceting process is weakening the slab that does exist. The surface hoar layer remains more problematic where recent or past wind loading had created a stiffer slab in the upper snowpack. Adding insult to injury, more deeply buried weak layers are more worrisome here. With a shallower snowpack than further north and west, and more rocky, wind-affected alpine terrain, there are more areas where these weak layers are closer to the surface.

Moving south to the Soldier & Wood River Valley zone, in the mountains above Ketchum and Hailey, plenty of weak snow exists but a strong slab is less common. You can avoid most avalanche hazard by staying off of wind-affected slopes where a stiffer snow surface exists. In the western portions of this zone, including the Soldiers and the mountains around Dollarhide Summit, a much more complex snowpack exists—one that has attributes of all the other zones. Avalanches occurred in the Soldiers on the early January surface hoar layer, and deeper weak layers may remain a concern similar to the Galena Summit & E Mtns zone. Throw in the recent wind events that have hit the Soldiers, and you have a real mixed bag of conditions. 

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