Bulletin d’avalanche

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

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

Points saillants

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 drastically reduce your risk of getting caught in an avalanche by sticking to wind-sheltered, mid-elevation terrain.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    The snowpack this season has been plagued by a number of persistent weak layers. The layer most likely to produce avalanches in this zone is the prominent layer of early-season facets buried beneath a dense, 3' thick slab. However, we can't rule out more recently formed weak layers consisting of facets, isolated surface hoar, and crusts that are buried about 2' deep. Slow but 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 neighboring Sawtooths & Western Smokys zone—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. Triggering a wind slab (see Problem #2 below) could step down into these persistent weak layers, resulting in a much larger avalanche. Long story short, you can greatly reduce your risk of triggering a large persistent slab avalanche (or a wind slab avalanche for that matter) by sticking to wind-sheltered, mid-elevation slopes.

    (2/13/2021) This intentionally-triggered avalanche above Titus Lake initiated in a wind slab and then stepped down to the weak snow near the ground. While this event is a week out, similar avalanches remain possible.

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Over the past week, this zone has received a slow but 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. Given the steady light snowfall, evidence of past wind may be hidden. You're more likely to trigger a persistent slab avalanche (Problem #1 above) on wind-loaded slopes, and a triggered wind slab could also step down to these deeper layers. 

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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