Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

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

Expect to find sensitive wind drifts of fresh snowfall in upper-elevation terrain today. These will be most common along higher ridgelines, but look for them on mid-slope terrain features such as ribs, gullies, and below cliff bands. Natural and human-triggered loose snow sluffs are also possible on steep slopes, even those that are sheltered.  Continue to exercise caution around and under large cornices, as a failure could trigger a very large avalanche breaking on deeply buried weak layers.  

Avalanche problems

  • Wind Slabs

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

    New snow will fall on a buffet of old snow surfaces today. Areas of winded snow will creep in on the breeze and grow larger and more reactive as you climb in elevation. Older wind slabs that may still react to your weight may become masked by the incoming snowfall.  Look for drifted and pillowed areas below ridgelines, cliff bands, and mid-slope features such as ribs, gullies, and breakovers. Surface texture and denser/stiffer snow are tell-tale signs of a loaded slope.

    ADDITIONAL DISCUSSION

    Snow will likely move easily today regardless of wind, so expect to move some loose snow if you choose mid to upper-elevation terrain, particularly on the south half of the compass. Though generally regarded as a "manageable" problem, loose snow can catch you by surprise in steeper terrain. Continue to give all cornices a wide margin and be careful along ridgelines, as they can break further back than expected. Limit exposure under or adjacent to them. Cornice fall is currently the most likely way to trigger a very large persistent slab avalanche. 

    Recent avalanche activity in the upper elevations of the Tetons.

     

  • Deep Persistent Slabs

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

    Hard slabs 3-5 feet thick overlay weak snow that formed earlier in the season. Shallow, rocky, & unsupported terrain on the north half of the compass is the terrain most likely to harbor this problem. Thin areas in the snowpack are more likely to act as trigger points and are most common in these locations. It is currently unlikely that a human would trigger one of these slabs. Larger triggers, like cornice fall or surface snow avalanches, still have the potential to impact weak layers buried deeply in the snowpack and initiate a much larger avalanche.

    (3/6/2024) Crown of a very large (D3) avalanche in the South Fork Teton Canyon. This slide was triggered by a cornice fall on the right side of the photo. The avalanche occurred in steep, rocky NE-facing terrain at 9400' and ran 2400' to the valley floor and broke many mature trees.

    Photo: Cameron Galt

Avalanche Discussion

Building on yesterday's discussion of risk management. Risk boils down to our exposure and vulnerability to a given hazard. Many of us have intuitive notions of these two things, but they become slippery when we try to pin them down in a few words.  Exposure is subjecting myself to potential consequences. If I ski a line with a wind slab problem, I am exposing myself to that problem, whether I know it or not. You are the master of your own exposure and can frequently reduce it at will. Vulnerability describes susceptibility to harm. If captured by said wind slab, will I end up with a slap on the wrist or take a nasty ride through trees or a terrain constriction? Managing our exposure and vulnerability allows us to mitigate the potential consequences of our actions. Not all consequences are equal, and how we manage them is what's important. Have a process to help guide your risk-taking. This can be a decision-making tool, framework, philosophy, or list. The process we use to make decisions will increase our chances of a positive outcome. It doesn't guarantee it, though. Smart people trying really hard also get bitten by black swans. And that's the nature of being a human in avalanche country. 

As a quick note, we've transitioned to messaging a true deep slab problem vs  persistent slab. A variety of weak snow surfaces formed throughout February, and though not long-lasting, while they had periods of activity, we chose to lump them all together into one problem. If you were going to trigger one, you'd probably trigger both, and neither would be very good. These layers have since melded into the rest of the 'pack (i.e., were smooshed). Snow from early December remains something we could not call "unreactive" and is located near the base of the snowpack. It continues to produce avalanches with each large storm or with a large trigger. Though you are very unlikely to trigger an avalanche on this layer unless you initiate a cornice or surface avalanche in the right spot, it will likely be an issue once things start warming rapidly as we approach April.  

   

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