Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 7 years ago.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

Highlights

Widespread weak layers continue to create dangerous avalanche conditions, particularly in wind-loaded terrain. Cracks shooting from your boards or sled are a sure sign that you’ve found a sensitive slope. Avalanches may be triggered remotely — from above, below, and to the sides of slopes.

Avalanche problems

  • Persistent Slabs

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

    Last week’s storm pushed our weak snowpack to its breaking point. Large natural avalanches occurred in this zone, wiping out much of the season’s snowpack. Chris and I were traveling on Cape Horn Mountain on Friday and we experienced widespread collapsing and cracking of the snowpack and triggered several avalanches from a safe, low angle ridge above.

    Conservative travel continues to be the name of the game. Keep your eyes peeled for obvious signs of instability, I suspect you won’t have to look hard. Watch for cracks shooting out from your sled or board and collapsing of the snowpack, both great indicators that the snow you are on is unstable. And remember that with this type of weak layer, triggering avalanches remotely — from above, below, and to the sides of slopes, is a very real possibility.

Avalanche Discussion

The mountains have not received significant accumulations of snow since Friday morning, but obvious signs of instability continue. On Saturday, two separate parties of skiers triggered avalanches in the Galena Summit area. That same day, a group of riders triggered an avalanche on a wind-loaded slope in the Soldier Mountains. On each of the past three days, as I traveled on ridgelines that we’re not exposed to avalanche hazard, I remotely triggered avalanches. These avalanches occurred in three different mountain ranges. Don’t skim over these details, take a minute to let them sink in.

A layer of surface hoar is the primary culprit of nearly all of the recently reported, human-triggered avalanche activity. This layer developed in the clear, cold days that followed the set of storms over the Thanksgiving holiday. I’ve found these weak, feathery crystals in the mountains spanning from Banner Summit, down to the Sawtooths and Western Smokys, across the valley into the White Clouds, south to Galena Pass, and further south into the Boulders. In short, I’ve found it everywhere I’ve looked. The nature of the snowpack varies widely across our forecast zones, but this layer is a disturbing constant. 

If you’re the kind of person who reads the two paragraphs above and thinks, “I wish there was more to worry about,” I’ve got great news for you.  Large, sugary grains of depth hoar can be found in the Sawtooths, Western Smokys, White Clouds, northern Boulders, and Banner Summit area. Yesterday in the White Clouds, I observed a 600-800’ wide avalanche that had failed just above the ground on this weak snow, wiping out the vast majority of the snowpack. Skiers in the Sawtooths yesterday reported unstable snowpack test results and widespread cracking and collapsing on this layer and they stuck to low angle slopes not threatened by avalanche terrain above.

The year is just getting going but the list of problems to worry about is long. Complex, overlapping patterns of weak snow are very difficult to deal with. The easiest solution is to exercise conservative route finding and decision making in your backcountry travels. I know, that’s not what you want to hear. It isn’t what I want to have to tell you. But we don’t have any input into the character of the snowpack; the only thing we have control over is ourselves.

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