Avalanche forecast

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

With new snowfall and wind, human triggered avalanches remain likely today. Weak layers of snow are now buried 1-3 feet below the snow surface on most aspects and elevations. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes. The avalanche hazard will increase throughout the day today as new snow accumulates and SW winds increase. Conservative decision making and cautious route finding are advised. 

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 Greys River area with WSW winds in the 15-20 mph range (gusts over 30 mph). 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
    Likely
    Size
    1–2

    Areas of faceted snow, crusts combined with facets, and buried surface hoar are widespread across all forecast zones but are concentrated in low to middle elevations. Field observations are consistently finding unstable conditions in snowpits, with failure and full propagation continuing to occur several days after new snowfall. Even more important, remote triggering was observed 2 days ago just south of the Tetons in the Snake River Range. Evaluate the snow in yours pits to see if there is a weak layer below and a slab above. This recipe can crack a long distance and fail above or well beside you. Lower elevations have less snow and less slab over these weak layers but remain dangerous, particular over terrain traps. 

    (12/7/2022)

    A BTAC forecaster intentionally triggered this avalanche while tracking down unstable snow in the Snake River Range.

    Photo: Gabrielle Antonioli

Avalanche Discussion

The mid November dry spell created widespread layers of weak snow and crusts on all aspects and elevations. Snowfall from October turned into depth hoar in select locations as well, forming a weak and unstable base of the snowpack. These problems are not going away any time soon, and areas that have avalanched could avalanche again. Cautious route finding and terrain assesment are essential in these conditions. 

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. 

Nearly every snowpit in the observations over the past several weeks has continued to propagate at the middle and upper elevation bands (around 7,500 to 10,000 feet). These areas include well traveled areas in the Tetons like Glory Bowl and the sidecountry terrain of Jackson Hole Mountain Resort. The results of avalanche mitigation on closed runs at Snow King on Tuesday, continued collapsing in the snowpack and a remotely triggered avalanche should serve as bullseye information.  These recent events are a good reminder that this  snowpack is extremely variable across the terrain with a level of complexity that makes assessment challenging. There is no doubt that luck has been playing a more important role than it should in the lack of human involvment in avalanches in recent days. 

The weak layers in the snowpack are persisting predominantly in the middle to lower elevations, dependent on the mountain range.  These pits are failing on a variety of weak layers found on both southerly and northerly aspects, and primarily hold a mix of thicker layers of small facets, and/or surface hoar.  A common theme appears to be high strength in extended column tests (high # of taps before failure) and fair structure (not the worst, not the best).  The slab above these weak layers can be significant and thick in some places which may make them harder to trigger, but it is possible to find thinner spots in our developing snowpack where you can trigger this layer. Low probability but high consequence scenarios like these are difficult to plan for and navigate around, leaving the aforementioned luck playing an outsized role in safe travel in the terrain.

 

Regions covered