Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

An avalanche fatality occurred in this zone yesterday, and conditions remain dangerous on steep, upper elevation slopes. A steady stream of new and windblown snow is creating sensitive wind drifts and loading buried weak layers. You can drastically reduce your risk of getting caught in an avalanche by sticking to wind-sheltered, mid-elevation terrain.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Over the past week, this zone has received a constant trickle of snowfall accompanied by light to moderate winds, and this pattern continued yesterday and overnight. The low-density nature of the new snow has made it easily transported by even light breezes. Almost all open or sparsely treed, upper elevation slopes have experienced at least some amount of wind loading over the past week.

    Wind slabs may be found near ridgelines or mid-slope in exposed terrain. Owing to the near-vertical nature of the Sawtooths, the wind tends to blow snow down cliff faces where it accumulates in spindrift slabs on aprons below. This zone has received enough snow over the past week that wind slab avalanches could be plenty dangerous on their own, but you're also more likely to trigger a persistent slab avalanche (Problem #2 below) on wind-loaded slopes.

    Long story short, you can greatly reduce your risk of triggering an avalanche of any variety by sticking to wind-sheltered, mid-elevation slopes.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    The snowpack this season has been plagued by a number of persistent weak layers. The layers most likely to produce avalanches in this zone are found in the top 2-4' of the snowpack, and consist of facets, isolated surface hoar, and crusts. The prominent early-season facet layer is buried 4-5' deep in this zone, making it much more difficult (but not impossible) to trigger. Nearly constant loading from light snowfall and wind over the past week are not giving these weak layers any relief.

    An avalanche fatality occurred yesterday in the Smiley Creek drainage—more details are in the Forecast Discussion below. This very large avalanche released on a persistent weak layer buried in late January. Given the uncertainty surrounding these weak layers, this does not seem to be the season to enter prime-time, consequential avalanche terrain. Each time we feel like things are improving, evidence of instability rears its head and we have to back off with our tail between our legs. 

    You are more likely to trigger an avalanche on upper elevation, "prime-time" slopes steeper than about 35 degrees. Most upper elevation slopes have received additional loading due to wind over the past few weeks, making them more dangerous. While triggering a wind slab (Problem #1 above) is more likely, a wind slab avalanche could step down into these persistent weak layers resulting in a much larger avalanche.

    (2/19/2021) Photo of a very large triggered avalanche that resulted in a fatality on Friday, February 19th, near the head of Smiley Creek. The snowmobile track of the victim is visible in the center of the photo. The avalanche released on a south aspect at 9100'.

Avalanche Discussion

We are saddened to report that an avalanche fatality occurred yesterday in Smiley Creek in the Western Smokys Mtns (7 miles S of Smiley Creek Lodge, 8 miles SW of Galena Summit). A group of visiting snowmobilers was riding near the head of the drainage. A portion of the group was playing on lower-angled terrain above the Smiley Creek Road when one rider broke off from the group and ascended an adjacent slope. While climbing the slope, he triggered a very large avalanche that broke 3-4' deep and over 500' wide. The rider was caught and carried by the avalanche. He deployed his airbag and was found on the surface by his partners, but had succumbed to the injuries he incurred during the slide.

The avalanche occurred on a south-facing slope at 9,100' and ran 1,000' vertically. The debris ran into a well-defined gully where it piled up to an estimated depth of 20-30'. The slope angle of the start zone was an estimated 35-40 degrees. The top portion of the avalanche path was wind-loaded, and this area has received nearly constant light snowfall over the past week. The avalanche fractured on a thin layer of faceted snow atop a slick crust that was buried by the late-January storm. In a crown profile lower in the avalanche path, we found this layer to be buried over 3' deep—the top 2' of the snowpack consisted of newer snow from the past week.

We performed a site investigation yesterday afternoon—watch the video. More details—including avalanche specifics, a map, and additional photos—can be found here. We extend our sincere condolences to the friends and family of the victim and greatly appreciate their willingness to talk to us about the event. A full accident report will be published in the coming days.

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