Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Heavy snowfall and wind have created dangerous avalanche conditions at middle and upper elevations. Natural avalanches are possible and weak layers will be most sensitive in steep wind affected terrain. It also remains possible for riders to trigger deeper avalanches that fail on weak snow in the middle of the snowpack. Use cautious route-finding and conservative decisions to maintain a wide safety margin around steep terrain as the snowpack adjusts to the new load.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    You are most likely to trigger an avalanche in new snow on slopes steeper than 30°. This problem exists at all elevations and on all aspects. The storm slab will be most sensitive in exposed areas and could break 1-2 feet deep.  Watch for shooting cracks and feel for cohesiveness and areas of increased density, particularly in more wind exposed areas. Hand shear tests and pole probing can give you an idea of density changes and cohesiveness. Jumping on small convexities and test slopes can be a great indicator of storm slab sensitivity. Choose conservative terrain less than 30° and be mindful of steep overhead slopes and terrain traps below you.

    Watch for loose dry avalanches in steep terrain where sluffing could knock you off your feet.

    (2/4/2024)

    Small pockets of new snow could be cut and avalanched easily on the old snow/new snow interface around 8-12 inches deep. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Recent wind and snow have formed sensitive wind slabs 10-20 inches thick at middle and upper elevations on lee aspects. You will find this problem in exposed terrain features at middle and upper elevations. Variable winds throughout this storm cycle have distributed this problem on multiple aspects including cross-loaded features at middle elevations. As you travel, watch for drifting and feel for denser snow. Pillows, cracking and collapsing are signs that this problem exists. Avoid steep, wind affected terrain and watch for continued loading and wind transport throughout the day in exposed areas. There is currently lots of snow available for transport.

    On Sunday, several skiers were caught and carried 1500 vertical feet by wind slabs in consequential terrain that involved significant injury and a helicopter evacuation. Wind slabs have continued to build since then.

    A recent wind slab avalanche on Taylor (2/4).

     

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Weak snow exists in the middle of the snowpack. It is 2-5 feet down above 7500 feet and most prevalent on shady aspects at mid and upper elevations.The likelihood of triggering an avalanche on this layer has been decreasing with time. However, with increased loading from the current storm cycle, this weak layer could be more sensitive.  You are most likely to trigger an avalanche in areas like steep convexities, rocky slopes and wind affected terrain. Signs of instability on this weak layer are mostly absent and tracks on a slope are not conclusive evidence that it is safe. Use cautious route-finding and avoid steep overhead slopes.

     

    A persistent slab avalanche that was remotely triggered yesterday (2/3) south of Teton Pass. Crown visible through trees

Avalanche Discussion

There are currently several avalanche problems to track, and with continued loading, the snowpack will become more sensitive to triggers.

Up to 3 feet of snow has accumulated in the Tetons since Friday. We received another 12 inches at upper elevations in the last 24 hrs. Upside-down snow conditions exist and the storm snow continues to settle from yesterday’s warm temperatures and increasing wind today. Lower elevations received light rain. At mid and upper elevations, there is a mid storm interface/density change down about 10-20 inches that is prone to easy shearing and several D1 natural avalanches were observed yesterday at upper elevations at this interface. This storm slab is also sitting on a variety of surfaces including the widespread crust that formed during the warm spell last week on all but mid and upper elevation shady aspects. 

Storm snow SWE has totalled up to 3 inches in some areas at upper elevations. While unlikely, it is possible that with the increased weight on the January 4th interface, an avalanche triggered in the storm slab could step down to weaker layers and propagate larger than anticipated. I expect this would be most likely in steep, shady, middle or upper elevation terrain where the crust from last week is thinner or nonexistent.

A persistent slab avalanche was remotely triggered on February 3rd in shaded north facing terrain at 8,700’. This avalanche was triggered by the 7th rider on a slope. This terrain is a good example of where this problem is most easily found and highlights how difficult it is to predict.

Travel advice remains simple. Dial back your slope angles and give yourself a safety margin around consequential terrain including steep gullies and terrain traps. Be patient and let the snowpack adjust to the new load.

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