Bulletin d’avalanche

Snake River Range

Bridger-Teton Avalanche Center
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Danger d’avalanche

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

Points saillants

Today it is important to identify wind loaded terrain where it is possible to trigger large avalanches. Large wind slab avalanches occurred naturally in the adjacent Teton zone two nights ago failing on weak layers buried beneath the recent snow. Look for signs of stiffened or hollow sounding snow, large drifts, and textured or cracking snow surfaces to identify wind loaded slopes.

 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    Periods of strong, sustained wind over the last 48 hours have formed stiff slabs up to 3’ deep on leeward and cross-loaded terrain. These wind slabs are sitting above persistent weak layers of facets that could break above you and travel far across the slope. Larger avalanches will be possible the higher you travel in elevation. Pay attention to the subtle clues of snow texture and hardness to identify wind loaded slopes and steer clear.

    (12/18/2024)

    Wind loaded slope on leeward terrain (E aspect) in the adjacent Big Hole mountains

  • Persistent Slabs

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

    Weak layers of facets are buried beneath 1-2’ soft slabs. These weak layers are persistent meaning that you can continue to trigger avalanches on steep terrain without additional snowfall. This problem is widespread across all aspects in the middle-upper elevations and most dangerous on wind loaded terrain and more well developed on NW-N-NE-E aspects. Watch out as warming temperatures today can change the characteristics of the overlying slab above weak layers and increase sensitivity. Evaluate the terrain carefully as even small avalanches can have serious consequences above terrain traps such as gullies, creeks, and trees.

    (12/15/2024)

    Remotely-triggered soft slabs failing on persistent weak layers.

    Photo: Bridger-Teton Avalanche Center

Avalanche Discussion

Over the last week, the Snake River Range has received at least 26" of snow with 2” of snow water equivalent. Wind intensity peaked after the snowfall, sustaining  20-40 mph with gusts to 50 mph out of the west/southwest. Prior to this storm, near-surface facets had developed where snow existed during a period of dry weather in early December. The combination of recent snow and wind above these weak layers has caused numerous avalanches. Over time, the number of avalanches have decreased, but the size has increased as a result of rapid wind loading. Slopes that were rapidly loaded by wind are the main concern today  as these slopes line up with north through east aspects that hold the most well developed weak layers. Seek out terrain sheltered from the wind to avoid this problem. We also can’t rule out the persistent slab problem above 7500’ on sheltered terrain, especially on very steep, rocky, or convex slopes. Although less likely, wind or persistent slab avalanches could be triggered remotely from gentle slopes above, below, or to the side of steep slopes. 

Low avalanche danger exists in the lower elevations as most slopes were bare of snow before the recent storms and lack persistent weak layers. Small wet loose avalanches are also possible by the afternoon on slopes directly facing the sun. Be aware that the snowpack is still thin and obstacles are lying just below the snow surfaces. It’s a long season ahead, caution is advised with thin snow coverage. Access to terrain is still difficult due to the low snow coverage in lower elevations. 

Régions couvertes