Bulletin d’avalanche

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Sat
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Avalanches are unlikely, and most slopes are safe. Watch for isolated wind drifts and cornices at upper elevations. Very steep slopes that directly face the sun could produce small, loose snow avalanches (sluffs). 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1

    Last weekend's wind and snowfall formed small drifts and slabs at upper elevations. Tuesday near the head of Beaver Creek, a skier triggered a small slab avalanche just below a corniced ridgeline (see photo). The slab failed on a subtle sun crust on an E-facing slope at about 10,000'. Triggering one of these small slabs remains a possibility today, particularly where they overlie facets associated with a crust. 

    Watch for smooth pillows of stiffer snow, dunes, or wave-like patterns on the surface. If the new snow depth rapidly increases and feels stiffer than loose powder, you've found a wind slab. Snowpack cracking is an obvious sign that you've found a sensitive drift. These slabs are unlikely to produce an avalanche large enough to bury a person, but triggering one in the wrong place could bring serious consequences.

    Cornices grew in the past couple weeks (photo), forming curls and overhangs in some exposed terrain. Give any large features a wide berth.

    ADDITIONAL DISCUSSIONLoose snow avalanches are possible today. These slides are most likely in very steep, sun-drenched, rocky terrain that's sheltered from the wind. Wet and sticky snow beneath your feet is a clue that the snow surface is weakening. 

Avalanche Discussion

As usual, the Sawtooths and Banner Summit boast the deepest snowpack in our forecast area. The big January storm (30-50” of snow in 5 days) overloaded the depth hoar and facets near the ground, producing a widespread, deep slab avalanche cycle. Since that storm, this area has received well below average snowfall. The weak layers responsible for the January avalanche cycle look a lot better than they did in January; for now, they are hibernating, or dormant. Also, the weak layers are buried far enough below the surface (typically well over 3 feet) to significantly reduce the chances of people triggering large avalanches.  

We now have what I like to call a "what-you-see-is-what-you-get" snowpack (WYSIWYG for short, or phonetically, "whizzy-wig"). Meaning, we're not likely to get surprised by deeper weak layers. Instead, the danger rises during a storm, subsides in the following days and we start over again, dealing mainly with new snow instabilities near the surface. The storm over the weekend built soft slabs in the alpine, one of which was triggered on Tuesday. Sun and warm temperatures are working to help those slabs heal. This time of year, warm sun following a storm will peel new snow off of very steep slopes that face the sun. Several "sun-induced" loose snow avalanches occurred in the last couple of days. The "easy pickings" are gone and naturally occurring loose snow avalanches are less likely today than they were yesterday. That said, if you find yourself in sticky, wet snow this afternoon don't be surprised if you're able to trigger a heavy, wet sluff in steeper terrain. 

There are lots of generally safe places to enjoy the day but a winter mountain environment is never devoid of avalanche danger. Continue to practice safe travel techniques: give cornices a wide berth, ski or ride one at a time, and keep an eye on each other. If you find a small sensitive slab, don't write it off as an "outlier". If something doesn't feel right, back off and come back another day. The consequences of even a small slide are amplified in extreme terrain. 

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