Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

You can trigger avalanches large enough to bury you on many steep slopes. Avalanches will be larger, more destructive, and easier to trigger as you gain elevation and climb into terrain affected by the wind. Some of these slides will fail on buried weak layers, producing very large, unsurvivable avalanches. These can be triggered from long distances away. Loose snow avalanches will release naturally during periods of direct sun.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    Weak layers in the snowpack were pushed to their breaking point by this week's storm (photo at right/above). On Thursday afternoon, I remotely triggered a large avalanche in a neighboring zone that failed on the prominent weak layer near the ground, leaving sharp rocks barely covered with depth hoar in its wake (video here). An additional 10-20 inches of snow fell since this avalanche. The slide broke 250 feet wide, ran over 1,000 feet, and is on the small side of what this snowpack can produce. Avalanches that fail on these layers can break thousands of feet wide and send the entire season's snowpack downslope. These slides can wipe out swaths of mature timber and will be unsurvivable. 

    Avalanches that fail on persistent weak layers behave in ways that surprise even experienced users. These slides will break wide, wrapping around entire bowls and cirques. You can trigger these avalanches from long distances away from steeper slopes, including from flat terrain below large avalanche paths. Any of the storm snow avalanches described below can trigger these much larger slides. 

    ADDITIONAL DISCUSSION: In the western portion of this zone, you'll find the early February weak layers buried underneath very dense and very heavy slabs. Triggering an avalanche on these deeper weak layers is less likely, but any slide that breaks on them will be massive. Smaller natural and human-triggered avalanches can step down to these deeper weak layers. Slides that break on these layers can wipe out swaths of mature timber and will be unsurvivable.

    This photo shows several large to very large avalanches that failed above the Baker Creek drainage, likely overnight Friday into Saturday. The crowns span hundreds of feet of terrain, and are an estimated 3-5 feet deep in places. Getting caught in an avalanche like this and being dragged through the trees below would likely be unsurvivable. This slope faces E-SE at 9,700'.

    Photo: Ben VandenBos

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2

    Up to 2 feet of settled snow have fallen in this zone since Wednesday (1.5-2 inches of SWE). You will encounter a wide range of problems related to this new snow today:

    SLABS: Large slabs failing within the new snow are likely, and can occur even in sheltered terrain. The size and sensitivity of these slabs will increase significantly as you climb into wind-affected terrain. If the snow you are moving through is anything but fluffy powder, you are traveling through wind-affected snow. Triggered slides will run fast and far on the stiff surfaces underneath, entraining significant amounts of snow and producing large debris piles. 

    LOOSE SNOW: Loose snow avalanches will be easy to trigger on all steep slopes. You can expect to see these slides happening naturally on slopes receiving direct sun. They'll start small but may become large as they pick up speed and material and rocket downslope. Loose snow slides can flank out into slabs, producing larger avalanches. 

    CORNICES: It has been a very windy week and there has been no shortage of snow available for the wind to blow around. Unstable cornices have grown quite large, and are struggling to hang on to their ridgeline homes. Be cautious when you are traveling on ridgelines, cornices will be easy to trigger and can behave in unpredictable ways. Large natural and human-triggered cornice failures will be effective triggers for large avalanches as they tumble downslope.

    Avalanches involving the recent snow will be large enough to bury you. Natural and triggered slides involving the new snow can be very effective triggers for the weak layers described below. Any avalanche that breaks down into these layers will be very large and destructive. 

Avalanche Discussion

Avalanche conditions vary widely across this zone. 

Coverage has remained thin all year in the mountains above the Wood River Valley. In areas holding snow, a very weak snowpack has been developing. The theme here is how quickly you can travel from a thin snowpack riddled with sagebrush into a snowpack that is teetering on the edge, waiting to send you and the entire snowpack downslope. This snowpack just received its biggest load of the year. During a smaller loading event earlier in the month, Sun Valley Ski Patrol reported triggering a very large avalanche that wiped out the entire snowpack (photo here). These are the types of slides we're worried about in the eastern portion of this zone.

In the Soldier Mtns, you'll find a much deeper snowpack. Here, the primary weak layers of concern are in the upper snowpack. Professionals at Soldier Mountain Cat Ski reported unstable snowpack test scores and triggered smaller avalanches on these layers in wind-loaded terrain in the past 10 days. The slab over these layers has become much thicker thanks to the storm, and triggering large persistent slab avalanches is likely on many slopes. Much larger persistent slab avalanches are also possible on deeper weak layers here. 

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