Bollettino valanghe

Banner Summit

Sawtooth Avalanche Center
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Pericolo valanghe

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

A steady stream of new and windblown snow is creating sensitive wind drifts and loading buried weak layers. Triggering an avalanche 1-3 feet deep is possible, especially on steep, upper elevation slopes. You can dramatically 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
    Possible
    Dimensione
    1–2

    Over the past 10 days, this zone has received a slow but steady trickle of snowfall accompanied by light to moderate winds. The low-density nature of the new snow has made it easily transported by even light breezes.  Wind slabs may be found near ridgelines or mid-slope in exposed terrain. The lower elevations of the Banner Summit zone mean that wind loading can be more subtle—assume that all open or sparsely treed, upper elevation slopes have experienced at least some amount of wind loading over the past week.

    ADDITIONAL DISCUSSION:A number of weak layers—both prominent and subtle—exist in the top 3' or so of the snowpack. None of these seem particularly reactive but have still produced a few small to medium-sized avalanches in the past week. Nearly constant loading from light snowfall and wind are not giving these weak layers any relief. One of these layers is the likely culprit behind the snowmobile-triggered avalanches near Cape Horn Summit last Tuesday (photo to right/above), and a skier Friday triggered a slide in very steep terrain. And we can't forget the early-season weak layer near the base of the snowpack. You'd have to be unlucky to trigger a slide this deep, but this layer has kept us out of the terrain where it is most likely to exist—namely very steep, rocky, and wind-affected terrain at upper elevations.

    You can greatly reduce your chances of triggering an avalanche of any variety by avoiding "prime-time" slopes over about 35 degrees, especially in wind-exposed upper elevation terrain.

    (2/16/2021) A snowmobiler triggered this avalanche from the bottom of the slope last Tuesday afternoon near Cape Horn Summit.

Avalanche Discussion

We are saddened to report that an avalanche fatality occurred Friday 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 Friday 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.

Another avalanche fatality occurred in southeast Idaho yesterday. Some preliminary details can be found in this news report. Information about all U.S. avalanche accidents can be found on Avalanche.org.

Regioni coperte