Bulletin d’avalanche

Tetons

Bridger-Teton Avalanche Center
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Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
Sans niveau
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Backcountry travelers have the ability to trigger large avalanches failing on weak snow near the ground. Steep, shaded terrain at the middle and upper elevations are most likely to produce a destructive avalanche. Carefully evaluate the snowpack structure before committing to a slope.

Problèmes avalancheux

  • Persistent Slabs

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

    Slabs of cohesive snow 2-3 feet thick overlay weak, faceted snow that formed during a dry period in November. Hard slab avalanches failing on this weak interface are most likely on west, north, and east aspects above 8,500’. Although a week of dry weather has made these slabs less sensitive to humans, the possibility of triggering a dangerous avalanche still exists. Predicting these avalanches is becoming more difficult as a slide may not release until several riders have ridden the slope. Previous tracks are not a good indication of stability with this problem. Collapsing the buried weak layer in a shallow portion of the snowpack, typically near rocks and sparse trees, is the best way to trigger one of these avalanches. If triggered, the resulting avalanche may be large, destructive, and pull out into lower angle terrain than expected. Maintain a wide margin around steep, rocky slopes that face away from the sun to avoid triggering a dangerous hard slab avalanche.

    A large avalanche near Phillips Pass that occured last week illustrates the current problem.

Avalanche Discussion

It has been 6 days since the last reported avalanche in the Tetons. Dry weather, diurnal heating/cooling, and time have made it more difficult to impact the weak layers at the base of the snowpack. However, continued reports of large collapses as well as propagating pit scores are evidence that the snowpack is unstable on shaded slopes at the middle and upper elevations. 

Triggering a large avalanche in steep terrain is still possible, especially if you happen to find the right shallow spot. Snow depths are highly variable and many slopes are littered with potential “trigger points''. Right now, committing to a steep slope with poor structure is committing to the uncertainty that you may trigger a destructive avalanche. Although the mountains have become quieter in recent days, it is important to remain vigilant and give steep, consequential slopes the respect they deserve. Time will continue to stabilize the snowpack, but for now choosing to ride lower angle terrain can help you avoid triggering a dangerous avalanche.

The current dry period is creating a variety of weak surfaces. Crusts are present on solar aspects while facets and surface hoar are forming on shaded aspects. Noting the characteristics of the snow surface now will help provide a better understanding of stability when snow returns to the area.

Régions couvertes