Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Continued heavy snowfall and strong wind are creating dangerous avalanche conditions. Avalanches are most likely on steep slopes with wind drifts or stiff snow on the surface but are also possible in terrain more sheltered from the wind. Although unlikely, some avalanches could fail on layers deep in the snowpack releasing a very large and unsurvivable avalanche.

Avalanche problems

  • Wind Slabs

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

    Expect to find wind slabs, large drifts, and cornices in upper elevation and exposed middle elevation terrain. This zone has picked up 12-20" of snow (1.3-1.7" SWE) since Monday night and another 3-8" (0.3-0.8" SWE) is in the forecast today. Triggering a wind slab is most likely near ridgelines, beneath cornices, and on the sides of cross-loaded gullies. 

    Strong wind has mixed down into valley locations as well, so don't be surprised to find stiffer, wind-drifted snow near the mouths of main drainages and near prominent terrain features lower on slopes. 

    Some of the wind slabs may have formed above weak snow in the upper part of the snowpack and could be more sensitive to triggering than you would expect. Cracks shooting out in front of you are a clear sign you could trigger wind slab avalanches. Pay attention to how the snow feels beneath your boards or sled. If you feel the snow stiffen or notice you're staying closer to the surface instead of sinking deep into the snowpack, you've found wind-affected snow and should avoid steep slopes. 

    Additional Discussion:Temperatures climbed steadily through the night and will reach near 40 F at the lowest elevations today. This warming could cause rapid settlement in recent storm snow enhancing your chance of triggering a slab avalanche on even wind-sheltered slopes at low elevations. These avalanches should be small but can have big consequences if they drag you into a terrain trap like a road cut or a creek bottom. 

  • Deep Persistent Slabs

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

    A mix of facets and crusts leftover from October snowfall make up the base of the snowpack on most shady middle and upper elevation slopes. Some sunnier, upper elevation aspects have this layer too. To the south of this zone, avalanches have failed on this layer following each major precipitation event.  Because this snow is now deeply buried, it has become much harder to impact it with our weight (see video to right).

    You are most likely to encounter this problem in alpine terrain where the snowpack is variable and thinner places in the slab give you "better access" to the weak layer. This same terrain is also getting loaded the most rapidly by ongoing snowfall and wind. While triggering one of these monsters is unlikely, it's nearly impossible to predict exactly which individual slopes are possible to trigger.

    How are local professionals managing this problem? They are generally taking it off the table by avoiding rocky, alpine terrain with variable snow depths, especially "prime time" slope angles over about 35 degrees. This travel strategy is pretty easy to swallow given the excellent riding and skiing conditions on other slopes.

Avalanche Discussion

Yesterday, snowfall along the Sawtooth and Smoky mountains just didn't want to quit. Storm totals since Monday evening are pushing well over 2' and will surpass 3' by the end of the day. As a result, the danger in the Sawtooth & western Smoky Mountains Zone has bumped to HIGH. Large, natural avalanches are likely and avalanche terrain should be avoided. Honorable mentions in neighboring zones include Dollarhide Summit and Galena Pass where similarly dangerous avalanche conditions exist. A sharp gradient in snowfall occurs as you move to the east and south of the Smokys. Far less snow fell in our southern and eastern mountains but dangerous avalanche conditions exist in winder terrain. 

Unlike the disparate snowfall amounts across the zones, it's been windy everywhere. Yesterday it sounded like a category 3 hurricane on top of Baker Pk. The Peak 2 weather station in the Soldiers recorded a gust of 123 mph and gusts topped 100 mph in 7 of the last 24 hours. Observers reported wind-blown snow anywhere from the high peaks to Highway 75 and the foothills above the valley floor. This wind affect built sensitive wind slabs yesterday, some of which failed naturally or were triggered by skiers. It also stiffened the snow surface on many slopes, increasing the odds of triggering a smaller, soft slab avalanche on some steep slopes. 

The final twist? It's eerily warm out there. Today's high temperatures will reach 40 F near Fairfield, Hailey, and Stanley. Near or slightly above freezing temperatures will also creep into middle elevations. This warming will act to condense the slab, stiffening the snow surface and creating top-heavy slabs on some lower elevation slopes. These slabs may peel off naturally or be sensitive to your weight. There's a lot of uncertainty here, amplified by the weak, shallower snowpack at lower elevations. Across the board, it's good to realize that conditions may change quickly as the day warms. Related to this concern, is the often overlooked hazard of roof avalanches. I saw a few steep, metal roofs release yesterday afternoon. If yours hasn't shed its snow, there's a good chance today is the day. 

Regions covered