Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Avalanche danger

Sun
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

The ongoing storm has created very dangerous avalanche conditions. You can easily trigger avalanches large enough to bury you on many steep slopes. These slides can be triggered from long distances away. Very large natural avalanches will continue to occur naturally and may impact valley bottom locations. We recommend you avoid all avalanche terrain today, including the run-out zones below avalanche paths. 

Avalanche problems

  • Storm Slabs

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

    Up to 1.5 feet of settled snow have fallen in this zone since Wednesday (1-1.5 inches of SWE). More is falling this morning. You will encounter a wide range of problems related to this new snow today:

    SLABS: Large slabs failing in the new snow are very likely. The size and sensitivity of these slabs will increase as you climb into wind-affected terrain. Thanks to the strength of the wind, you can expect to see wind slabs at all elevations, though they will be smaller on lower elevation slopes. If the snow you are moving through is anything but fluffy powder, you are traveling in wind affected terrain. Enough snow has fallen that sensitive slabs are lurking even in sheltered terrain. Triggered slides will run fast and far on the stiff surfaces underneath. 

    LOOSE SNOW: Small loose snow avalanches will be easy to trigger on all steep slopes. If the sun makes an appearance for long this afternoon you can expect to see many of 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. 

    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, threatening the starting zones below. Be cautious when you are traveling on ridgelines, cornices will be easy to trigger and can behave in unpredictable ways. Large cornices can fail naturally at any point today. These beasts are very effective triggers for large slab 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 above. Any avalanche that breaks down into these layers will be large and destructive. 

  • Persistent Slabs

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

    Weak layers in the snowpack are being pushed to and past their breaking point by the ongoing storm. On Thursday, 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 at right/above). This slide broke 250 feet wide, ran over 1,000 feet, and is on the small side of what this snowpack can produce. Avalanches that break thousands of feet wide and send the entire season's snowpack downslope are expected to continue occurring naturally today. 

    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: Deeper weak layers exist in the snowpack in the western portion of this zone. You'll find these layers buried underneath the very dense and very heavy slabs that formed from snow in the month of February. Smaller natural and human-triggered avalanches can step down to these weak layers, producing much larger avalanches. Slides that break on these layers can wipe out swaths of mature timber and will be unsurvivable. 

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 is currently receiving 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. 

Your strategy for not getting caught in an avalanche today is simple: just stay out of the way. 

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