Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Close to a foot of new snow from yesterday, with continued snow today, paired with moderate to strong westerly winds will build new firm, cohesive slabs in exposed terrain that could be easily triggered by a skier or rider. This new snow will also add stress to weak layers buried 3 feet below the surface. Look for evidence of wind slabs such as drifts, stiffened surfaces, or cracking while using cautious decision making in avalanche terrain as buried weak layers adjust to the new load. 

Avalanche problems

  • Wind Slabs

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

    10” of new snow combined with westerly winds 20-30 mph and gusts to nearly 50 mph has built firm, cohesive wind slabs in the middle and upper elevations. These wind slabs will be concentrated to mainly the easterly half of the compass. Slab depths could be up to 2 feet. An additional 2-4 inches of snow today, with areas of higher amounts due to localized banding, will increase the sensitivity of these slabs as winds continue to transport snow. Changing wind direction will alter where these slabs develop as well. Terrain with a southerly component could also see increased sensitivity as new snow falls on top of slick crusts. Be aware that triggering a wind slab could create a step down effect on buried weak layers (Problem #2) resulting in a very large avalanche. 

    (1/29/2023)

    Obvious sign of instability. Look for cracking today similiar to this to help identify wind slabs. 

    Photo: Drinkard

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    The January 26th storm buried weak layers of snow, creating the possibility of triggering slabs 2-3 feet deep that could be soft or hard depending on the location. These weak layers vary in distribution and have been more sensitive in terrain with a southerly component that harbors a facet and crust combination. Avalanche activity on this layer has decreased over time, but new snow over the last 24 hours will add stress to these weak layers and increase the likelihood of triggering. Use extra caution in terrain with higher amounts of new snow, such as the upper elevations or fresh wind loaded zones. 

    Deep Persistent Slab: A weak layer of snow highlighted by the November 27 crust/facet combination is present on previously wind scoured aspects (W-S-SE) in the middle and upper elevations. Triggering an avalanche on this layer is very unlikely as it appears dormant; however, a very slight risk remains, such as another triggered avalanche or impacting a very shallow thin spot, for triggering a very large avalanche up to 5 feet deep causing severe consequences.

Avalanche Discussion

Quick Pulse of Pow

Until yesterday, the Forecast Area hadn't received any new snow since the major storm cycle on January 26th, which buried weak layers highlighted as our persistent slab problem. Avalanche activity has decreased without any reports of human triggered avalanches over the last several days. Let’s keep this good streak rolling and use cautious decision making today as new snow evolves the complexity of the snowpack. A mixed bundle of poor interfaces for wind and persistent slabs to avalanche exist due to large variability across different aspects. This creates a high amount of uncertainty in how all these weak layers will adapt to the new load. Multiple layers of hard crusts and/or facets now exist within the snowpack, creating poor interfaces between storm snow, wind slabs, and persistent slabs. Terrain with a southerly component and melt freeze crusts will likely be the most reactive, both in terms of new snow instability and buried weak layers. Near surface facets are also a concern on W to E aspects. Dig down in the snow, identify these layers and perform stability tests to increase your safety margins. Veering winds of moderate intensity will also compound the ability to easily manage terrain and predict where slabs are forming.  With all these factors combined, today seems like a suitable day to let the snowpack chill out while we enjoy the fresh powder in low consequence terrain.

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