Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

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

Triggering a large, destructive avalanche remains a distinct possibility today. Layers of weak snow are buried beneath a thick, dense slab of snow. Avalanches may be triggered from long distances away from steeper slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Triggering a 2.5-3.5' thick persistent slab avalanche is possible on many slopes. Persistent weak layers (sugary facets, surface hoar, or crusts) exist on most aspects and elevations. The recent storm added to the slab everywhere, and the weak layers are widespread. This means you could trigger a large, dangerous avalanche on just about any steep slope you encounter, even at lower elevations and in terrain sheltered from the wind.

    Persistent slabs are tricky. While recently wind-loaded slopes are likely more dangerous, you can't simply look for and avoid obvious wind drifts. The slab is harder and denser near Banner Summit than in our other zones, making it a little less sensitive to triggering by skiers and snowmobilers. This means you may not experience as many obvious signs of instability like snowpack cracking or collapsing. However, when you do find the "sweet spot" remember that you could trigger slides remotely—from gentler terrain above, below, and to the sides of steep slopes. These avalanches may break wider than expected or higher on the slope above you. 

    Unfortunately, avoiding slopes steep enough to slide is the only way to effectively manage this problem. Skiing or riding steep, consequential terrain remains a risky roll of the dice.

    ADDITIONAL DISCUSSION: Wind speeds increased for about 6 hours last night before calming back down. There is plenty of snow to move around and some slabs likely formed in exposed terrain. Though relatively thin, I expect these to be touchy. The wind will pick up again this afternoon and another round of slabs will be forming. Triggering one of these slabs can make for an effective trigger for avalanches failing on deeper weak layers. 

    (12/12/2022) In the Banner Summit zone, the weak November snow is buried beneath a 3' thick dense slab. 

Avalanche Discussion

The intense storm that blanketed our area drew to a close 5 days ago. This snow fell on an exceptionally weak snowpack that developed during early-season droughts. The resulting avalanche cycle was truly impressive. Hundreds of large avalanches occurred, on slopes from the valley floors all the way to the mountaintops. Houses were hit, the Big Wood River was dammed by avalanche debris, and multiple human-triggered avalanches occurred. It's hard to drive around or ride through the mountains and not see the aftermath of an avalanche.

The snowpack has been getting a much-needed break the past few days, allowing the healing process to begin. Unfortunately, this is not a fast process. Thanks to the whims of physics and the properties of water, weak layers form far more quickly than they heal. I'm optimistic that we can put these weak layers behind us, but I'm confident that we haven't done that yet.

I wouldn't be an honest man if I told you that waiting for stability to improve is easy. Standing in the sun and looking at steep slopes covered in perfect powder and deciding not to ski or ride them is flat-out hard. Trust me, I know. Nothing brings me more joy than playing in steep terrain on snow-covered mountains. But that's not where you will find me this weekend. The chance of triggering large, destructive avalanches is far too great. Instead, I'll be searching out low-angle ridgelines for skiing and deep, powdery meadows for riding, all while paying close attention to the terrain above me. I strongly encourage you to do the same. We are all lucky that this region provides plenty of opportunities for both. 

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