Avalanche forecast

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Sawtooth Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Conditions are dangerous at upper elevations. Expect to trigger large, 1-3 foot thick avalanches where the wind has drifted snow or stiffened the snow surface. Avalanches may release naturally. Triggering similar slides in more sheltered terrain is not out of the question.

Avalanche problems

  • Wind Slabs

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

    What is it? You are likely to trigger sensitive 2-3 feet thick slabs with last night's moderate winds and additional new snow. Expect to find these soft and hard slabs to be most sensitive in exposed middle and upper elevations. Over the past week, multiple large natural and human-triggered avalanches released in wind-loaded terrain in the Sawtooths and Smokys (photo above/right, list).  On Saturday, a rider in the Pole Creek drainage triggered a large wind slab that broke above them on the slope they were riding (observation here). Importantly, this slide occurred before the added load from recent snow and wind.

    Where is it? You'll likely find slabs in upper-elevation terrain, near ridgelines, and mid-slope terrain features like ribs and gullies. Slabs may extend down into middle-elevation terrain in areas where the wind has been blowing harder.

    How can you recognize it? Look for shooting cracks extending out from your skis or sled, which is an obvious sign of instability. Watch for drifts, dunes, and ripples on the snow surface. Wind slabs can have a smooth, chalky appearance and feel and sound hollow, like a drum. Wind-deposited snow will be stiffer and keep your skis or snowmobile on or closer to the surface. Some of these slabs might be masked by recent snow and be more hidden.    

    How can you manage it? You can significantly reduce your risk today by steering clear of wind-loaded terrain. Today's slabs might not behave like your "typical" wind slab. Various weak layers exist in the snowpack's upper 1-2 feet (watch the video at right/above). Because of this weak snow, today's slabs may break wider and deeper than expected from a "simple" wind slab.

    ADDITIONAL DISCUSSION: The layers of weak snow in the snowpack's upper 2-2.5 feet are being pushed toward their breaking points. Up to this point, we've needed the additional weight and stiffness from wind loading to make avalanches on these layers. Wind slabs and loose avalanches (sluffs) can step down into these deeper layers, releasing a larger avalanche than expected. Shooting cracks and collapses are indicators that you are moving on unstable snow. You are more likely to trigger these avalanches on slopes greater than 35 degrees in more sheltered slopes. See the forecast Discussion below for more details.

Avalanche Discussion

Over the last 48 hours, over 13 inches of snow have fallen here. Last night the winds picked up and likely made easy work of moving this light, fluffy snow. Today's most sensitive terrain is where this snow is being picked up and creating wind slabs. Carefully evaluate the terrain you are planning on going to play on today. To drive your terrain choices, be attentive to signs of instability, such as shooting cracks, collapses, and recent avalanches. If you are seeing or hearing these signs, chances are great that you are on unstable snow. Seek more sheltered slopes under 35 degrees to lower your chances of triggering large avalanches. 

Yesterday, a party of snowmobilers in the Sawtooths (report), remotely triggered an avalanche on a slope steeper than about 35 degrees below a band of cliffs. It took them about 5-7 passes going up the same slope before they could trigger the avalanche. Luckily, the avalanche wasn't big enough to bury them. Since then, the mountains received another round of snow with moderate to strong wind. That means the slabs are growing in thickness and size from this example. The recently triggered avalanches have all been driven by wind. They are showing signs of acting more like a persistent slab problem, where they can be remotely triggered from gentle slopes nearby or from below and sometimes it won't be the first person on the slope to trigger it. Keep your head on a swivel today, as more snow is in the forecast, along with more wind. This will keep the stability from improving anytime soon. 

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