Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

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

Human triggered avalanches are possible at the middle and upper elevations today, especially where recent snow has drifted into stiff slabs of snow that overlie buried weak layers. Steep, rocky, wind affected, and shallow areas are the most likely zones to trigger slabs. Monitor the influence of the sun today and minimize exposure times on steep sunlit slopes. You can use tools such as probes and shovels to determine whether or not buried weak layers exist on the slopes you plan to ski or ride. 

Avalanche problems

  • Wind Slabs

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

    Variable winds over the last 24 hours have created wind slabs at the upper elevations that are 1-2 feet deep. Slabs could be both soft and hard. Northerly and westerly winds are forecasted for today, causing abnormal loading patterns.

    Moniter the wind direction and pay attention to signs of instability such as cracking within wind drifted snow.

    (1/17/2023)

    Small wind slabs triggered in Chicken Scratch (NE aspect off of Mt. Glory in the Teton Zone). 

    Photo: L. Wolfe

  • Deep Persistent Slabs

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

    The November 27 crust/facet combination is the highlight of a weak basal snowpack on W through E aspects at the middle and upper elevations. Be cautious in steep, rocky areas with thin snow coverage where large portions of the snowpack are weak and faceted. 

    Use your shovel and probe to determine if buried weak layers exists. Pay attention to signs of instability such as audible collapsing of the snowpack.

    (1/16/2023)

    This avalanche was triggered on a west aspect off of Albright Peak around 10,000 feet.

    Photo: C. Martin

Avalanche Discussion

Transition to Deep Slab Instability: Forecasters at the BTAC have chosen to categorize the current persistent weak layer problem as a Deep Persistent Slab avalanche problem as defined by the Conceptual Model of Avalanche Hazard (Statham et al, 2017). Characteristics of a Deep Persistent Slab include periods of avalanche activity followed by periods of dormancy, structure that is conducive to failure initiation and crack propagation, and incremental building of the overlying slab over many storm cycles. While there are no definite depth restrictions of a Deep Persistent Slab, previous research has looked at events with minimum crown depths ranging from 0.8 to 1.2 meters (Conlan and Jamieson, 2016; Conlan et al., 2014; Marienthal et al., 2015; Savage, 2006). The aforementioned snow structure characteristics more accurately describe the current snowpack setup (highlighted by the November 27 crust/facet combination) than a standard persistent weak layer.  

The Tetons are currently at the tail end of an incremental loading pattern, with dry Northerly flow residing over the area. You are most likely to trigger an avalanche where wind slabs lie on top of buried weak layers in steep, shallow, and rocky areas. Be mindful of the influence of the sun today. 

There was a human triggered avalanche on the west face of Albright Peak on January 16th that involved a buried persistent weak layer. Natural avalanches have been limited to new snow instabilities and wind slabs over the last week. 

Current snow surfaces are made up of low density stellars and near surface facets in many locations. Buried persistent weak layers from late November and early December are buried over 1.5 meters deep on leeward aspects. On wind exposed aspects these layers can be found much closer to the surface and are reacting in the moderate to hard range in stability tests. 

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