Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Dangerous avalanche conditions exist. Human-triggered avalanches involving dense, 1-4 foot thick slabs of snow are likely. Avalanches may be very large and destructive and can be triggered from long distances away from steeper slopes. Conservative terrain selection is encouraged today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Friday's storm brought 20-28" of snow (1.8-2.3" of SWE) to this zone. Snowfall was accompanied by strong winds blowing out of the SE-S-SW. This combination built very large, dense, 1-3 foot thick wind slabs on many slopes. Triggering a wind slab avalanche large enough to bury you remains likely today.

    Wind slabs will be largest and most broadly distributed in upper and middle elevation terrain. Wind slabs commonly form along ridgelines and near mid-slope terrain features like ribs and gullies. Large slabs also build at the base of large cliffs and on aprons below couloirs during storms, a common occurrence in the Sawtooths.

    Wind slabs and cornices that fail can be very effective triggers for the enormous, destructive persistent slab avalanches described below in Problem 2. 

    (3/11/2023) These avalacnhes failed in heavily wind-loaded terrain in the Boulder Mountains. They failed on a SE-facing slope at 9,600'. Note the obvious dunes visible in the snow surface above the crown.

  • Persistent Slabs

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

    Weak layers are buried underneath dense, 2-4 foot thick slabs of snow in this zone. This combination can produce very large avalanches capable of destroying a house. If you dig down, you'll find facet+crust combinations on slopes that face the sun and thicker stacks of weak facets on shaded slopes. Yesterday, an observer near Smiley Creek reported seeing multiple avalanches that had failed naturally on Eureka Peak in the Western Smokys. These slides broke hundreds of feet wide on E-NE facing slopes.

    Avalanches that fail on these layers can break very wide, wrapping around multiple aspects and connecting multiple avalanche paths (see photo at right/above). These slides can run the length of an avalanche path, impacting flat terrain long distances away from steeper slopes. 

    Managing persistent slab problems is difficult. If you want to completely eliminate the risk of triggering one of these beasts you'll have to avoid avalanche terrain. You can reduce (but not eliminate) your risk by choosing gentler slopes that are sheltered from the effects of the wind. And don't forget to pay attention to what is above you, these avalanches can be triggered from long distances away from steeper slopes. 

    (3/11/2023) This very large persistent slab avalanche was observed in the Boulder Mountains. It failed over 3,000' wide, wrapping around S-SE-E-NE aspects between 10,000' and 10,800'.

Avalanche Discussion

Friday's storm produced a truly impressive cycle of natural avalanches (video here). Avalanche activity was much most pronounced in our Galena Summit and Eastern Mtns and Soldier and Wood River Valley Mtns forecast zones. Head over to our Avalanche Database (map, list) to browse through some of these, we've entered about 200 avalanches large enough to bury you that occurred since Friday. Notable avalanches include slides on Della and Carbonate Mountains west of Hailey that dammed the Big Wood River (photo here) and hit several houses (photo here). We observed a number of very large natural avalanches in the Boulder and Smoky Mountains that broke thousands of feet wide (photo here). Natural avalanche activity was most widespread on Friday, though Scott observed 5 large natural avalanches that released in the Wood River Valley yesterday as well (observation here).

The Avalanche Warnings have expired, but conditions remain dangerous. Avalanche accidents commonly occur during the period of decreasing danger following major loading events. This is exactly where we find ourselves today. The mountains may not be crashing down like they did on Friday, but that doesn't mean it's time to let your guard down. Human-triggered avalanches remain likely, and the slides you trigger will not be small. Spend a few minutes browsing through the Avalanche Database to get a sense for the types of avalanches you might see and/or trigger out there. 

I recommend you head into the mountains with a conservative mindset today. If you are dead set on entering avalanche terrain, choose terrain where the consequences of being caught in an avalanche are lower. Your likelihood of surviving an encounter with an avalanche is greater in terrain free of terrain traps (creek bottoms, trees, rocks). If you just want to be outside in the mountains and come home safely tonight there are lots of great options; the skiing and riding are excellent in low angle terrain right now. 

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