Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 7 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Wind events over the past week have blown the recent snowfall into slabs and drifts in upper elevation terrain. Avoid steep slopes where you find wind-drifted or pillowed snow. Slopes where you could trigger weak layers buried 4-6 feet deep are becoming few and far between, but it may remain possible on very steep, rocky, wind-affected slopes at upper elevations. 

Avalanche problems

  • Wind Slabs

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

    The wind events of the past week have finally ceased, but we'll continue to deal with the aftermath for a few more days. These strong winds produced a number of small to medium-sized natural and triggered wind slab avalanches across the forecast area.

    Fortunately, these wind slabs will be easy to identify. Watch for snow that is denser than snow found on wind-sheltered slopes and tell-tale clues such as surface texture and a pillowed, drifted appearance. These will be less sensitive today, but I'd still avoid steep slopes where you find these indications of recent wind loading.

    ADDITIONAL DISCUSSIONTriggering a 4-6 foot thick persistent slab avalanche has become very unlikely. The weak layers we've struggled with all winter have not gone away, but they're buried at a depth where they are very difficult to impact with the weight of a skier or rider. Hard to trigger is not the same as impossible—you'll do well to keep them in mind and continue to factor them into your decision-making.

Avalanche Discussion

As we enter the first period of stable weather in quite some time, it's a good time to do a "State of the Union" on our current snowpack. 

The Soldier & Wood River Valley snowpack is the shallowest and weakest, especially in the mountains above Ketchum and Hailey. As is not uncommon in this area, there is plenty of weak, faceted snow—what's lacking is a slab of cohesive snow atop it. Unstable slopes are largely limited to where recent and/or past wind events have created dense or stiff snow in the upper pack. This was the case with a slide triggered during control work last week on Baldy. Storms earlier this winter favored the western half of this zone, and the snowpack there is more similar to Galena Summit.

The deepest snowpack exists in the Sawtooth & Western Smokys and Banner Summit zones. While these areas had thin snow at the start of the winter, they were heavily favored by the extended storm cycle at the start of the New Year. The early season weak layers are buried 4-6 feet deep, meaning that triggering an avalanche is difficult but likely unsurvivable. Avoiding thinner "trigger points" is the name of the game—these are more likely to be found in very steep, rocky, alpine terrain that is prevalent in the Sawtooths but less so in the Banner Summit area.

Finally, the Galena Summit & Eastern Mtns zone is the monkey in the middle. There is a great deal of variability across this zone, but it all falls somewhere between the two scenarios described above. The thin, windswept snowpack of the Boulder and Pioneer Mountains has characteristics of the Wood River Valley, where wind slabs sitting atop weak, faceted snow are the main concern. The Smoky Mtns of Galena Summit and the Baker Creek area have a bit deeper snowpack, with early-season weak layers buried 2-4 feet deep. In the White Clouds, the faceted snow near the ground seems especially pronounced—just a week ago, a monster broke over 500 feet wide and 4-6 feet thick.

So there you have it—the current State of the Snowpack. Just don't rip it in half...

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