Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Wed
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Out of date — this forecast expired 3 years ago.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, warming temperatures, and sustained winds have created dangerous avalanche conditions at middle and upper elevations. Slabs will be most sensitive in wind affected, upper elevation terrain. It 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

    Up to 2 feet of snow has accumulated in the Tetons since Friday. You are most likely to trigger an avalanche on slopes steeper than 30°. Upside-down conditions exist  and warming temperatures throughout the day will continue to settle the new snow into a more cohesive slab. This storm slab is sitting on a variety of surfaces including the widespread, slippery crust that formed during the warm spell last week on all aspects up to 10,000 feet. There is also a mid-storm interface down 8-10 inches in many locations that may be more prone to easy shearing. 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°.

    Storm snow SWE has totalled over 1.5 inches in some areas. 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, upper elevation terrain where the crust from last week is thinner or nonexistent.

    Finally, with the new snow, watch out for sluffing in steep terrain that could entrain enough snow to 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 8-18” thick at middle and upper elevations on lee aspects. You will find this problem in exposed terrain features at middle and upper elevations. Light to moderate south winds yesterday , combined with west winds 48 hours ago have distributed this problem on multiple aspects including crossloaded features at mid elevations. In places, these slabs have stacked on previous slabs to deeper depths up to 2 feet. 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.

    Several skiers were caught and carried by wind slabs on Sunday. 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 2-4 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, the snowpack is being loaded by the current storm and could be more sensitive, particularly in thin 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 was triggered remotely 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 at its worst and highlights its difficult to predict nature.

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

Avalanche Discussion

Having a mental model of the current snowpack will help with decision making and with what to look for as you move through the terrain and cross elevation bands.  Keep in mind the character of the 3 different avalanche problems today, and perhaps more importantly, how to approach making terrain decisions based on what you find as you travel.  Here is a recap.

  • The storm slab problem is #`1 on the radar. It is widespread and as snow settles and warms today, it will become more reactive. Direct feedback will be obvious and include cracking and collapsing. Small, inconsequential test slopes are great indicators of the problem.
  • The wind slab problem is specific to exposed upper elevation terrain and cross loaded features at middle elevations. You may see the same clues as the storm slab including cracking and collapsing. Also look for obvious pillows and denser drifts. Travel in sheltered terrain to avoid this problem.
  • The nagging persistent slab problem exists in many places but is trending towards unlikely. Middle and upper elevation shady aspects are the most suspect. You probably won't see signs of instability until you trigger an avalanche, however unlikely. Digging and probing are the only ways of determining where this problem is. Keep in mind that new snow continues to stress these weak layers.

Travel advice is simple today. Dial back your slope angles and give yourself a safety margin around consequential terrain including steep gullies and terrain traps.

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