Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The combination of new snow, wind, and buried weak layers will make human triggered avalanches possible today. The avalanche hazard will increase throughout the day today as new snow accumulates and SW winds increase. Cracking within wind drifted snow and collapsing of the snowpack are warning signs of heightened avalanche conditions. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    New snow and wind will combine throughout the day to form reactive wind slabs in NW through SE terrain at the middle and upper elevations. 2-4 inches of snow is expected throughout the day above 8k' in the Tetons with WSW winds in the 15-20 mph range (gusts over 30 mph). Up to 6 inches of snow is possible at the upper elevations by early this evening. Moderately cold temperatures are expected along with the wind. With available snow for transport from previous storms, slab depths could reach 1-2 ft in favorable locations. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    The November 27th Layer is now buried 2-4 feet down from the surface of the snow at the middle and upper elevations. At the lower elevations this layer is 1-2 feet down on all but Southerly aspects. Human triggered avalanches remain possible, especially at the middle and lower elevations where it is closer to the surface. Field observations are consistently finding unstable conditions in snowpits, with failure and full propagation continuing to occur several days after new snowfall. New snowfall and wind will add stress to this layer, although natural avalanches remain unlikely today. 

     

Avalanche Discussion

A shortwave trough will impact the forecast area today through early tonight. Snowfall amounts in the 2-4 inch range with WSW winds in the 15-20 mph range are forecasted, but the upper elevations could see more. This trough precedes a much larger closed low system that is currently off the coast of British Columbia. New snow and wind will combine today to form fresh wind slabs with new/pre-existing snow. This new snow will also stress buried weak layers, though to what degree remains uncertain. 

The Teton Trickle over the last few days left the range covered with about a foot of low density snow. This snow received a zipper crust on Southerly aspects on December 7 which should limit the available snow for transport. The November 27 layer (mid November dry spell) is now buried 2-4 feet below the surface of the snow. This layer is composed of crust facet combinations on S, E, and W aspects. On Northerly aspects this layer is made up of near surface facets and even some surface hoar in some locations. Field observations continue to reveal unstable test results with this layer in snowpits. Lower elevations have the poorest structure but generally lack slab qualities that are favorable for avalanches (exceptions abound).

So far Triple Dip La Nina conditions are treating the Tetons favorably. Current snow water equivalent measurements show Grand Targhee to be 114% of median value while Phillips Bench sits at 130% of median. The Togwotee Pass snotel is at 95% of median and Willow Creek in the Salt River Range is 135% of median. 

Regions covered