Bulletin d’avalanche

Tetons

Bridger-Teton Avalanche Center
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Danger d’avalanche

Tue
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Triggering an avalanche is unlikely today. Sheltered and shady slopes at the upper elevations that held snow prior to November 2 are a lingering concern.  Remember that it is early season out there and any avalanche involvement could result in traumatic injury.

Problèmes avalancheux

  • Persistent Slabs

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

    This weak layer of snow first covered on November 2 is now buried by 1-3 feet of snow at the middle and upper elevations of the Tetons. Observations from upper elevations in the Tetons, Togwotee and Greys have been limited, so there is some lingering uncertainty the stability of this layer there, particualrly in steep, rocky terrain. In those locations, triggering the weak layer from a relativiely thin spot that then propagates a crack into a thicker slab would be the concern. Dig a pit to identify and test for reactivity in this weak layer of snow and find another slope to recreate on if the snowpack collapses. No avalanches have been observed on this layer at the middle elevations since November 5 in the Tetons. 

     

    Snow settliing  well with weak layer (55cm down)  gaining strength. ECTX. Density breaks also stubborn to unreactive. D1 or smaller wet loose activity near rocks.  2cm crust on sunlit surfaces. 

Avalanche Discussion

Triggering an avalanche on this layer has become unlikely. These are the areas where poor snowpack structure is mostly likely to exist. Dig a quick pit and perform an extended column test on safe slopes that are representative of the ones you plan to ski or ride. Human triggered avalanches were observed on this layer on November 5 at Grand Targhee, and explosive triggered avalanches involving this layer were observed at JHMR on November 9 with no results on this layer during mitigation efforts at Grand Targhee on Friday, Nov 11. Natural activity on this layer was minimal throughout this last major storm cycle. Since November 4, around 5 inches of snow water equivalent has fallen on this layer at the upper elevations.  

The Tetons picked up snow every day from November 2 to November 11. To top it off, orographic convection really kicked in on November 10 with favored locations picking up well over a foot of low density snow. In this time period around 5 inches of snow water equivalent has accumulated at the upper elevations. All of the snow (and even a little rain) fell on weak snow and crusts that were formed from October 28-November 2. During the beginning of the cycle human triggered avalanches were observed at Grand Targhee. Widepread collapsing and cracking were observed on this layer throughout the storm cycle on Teton Pass, as well as avalanches within the new snow and its various density changes. Explosive triggered avalanches were observed at JHMR, with some apparently reaching down to the November 2 layer. No activity has been observed on this suspect interface since November 9, but there is still some uncertainty around its reactivity in high, rocky terrain. The lack of natural activity on the November 2 layer throughout the barrage of storms was curious. This layer is mostly composed of 1-2 mm facets with a few larger ones thrown in for good measure. It could possibly contain preserved surface hoar in some protected locations, but this seems unlikely after 5 inches of water has been dumped on it. 

Régions couvertes