Lawinenlagebericht

Tetons

Bridger-Teton Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Dangerous avalanche conditions exist, especially on wind-loaded slopes. Significant amounts of snowfall and wind have buried weaker snow beneath 3+ feet of dense snow. Numerous large and destructive avalanches have been triggered by humans over the past several days. Triggering an avalanche remains likely and can occur in wind-sheltered terrain as well as from gentler terrain above, below, and to the sides of steeper slopes. 

A large avalanche triggered by several parties on Mt. Taylor yesterday illustrates the seriousness of this hazard. Skier-triggered avalanche on Mt. Taylor

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–3

    Yesterday in the Tetons and Togwotee Pass zones, I observed optimal wind speeds for transporting copious amounts of new snow. I found both stiff and soft drifts of windblown snow, and these cracked easily under my weight. I'd expect these to be less touchy today, but you'll want to avoid any slope with wind-drifted snow. We have received enough new snow that these slabs could produce a large enough avalanche to bury you and break 3-4+ feet in depth. Additionally, there is the possibility of a slide stepping down into the deeper persistent weak layers described below. 

    It pays to recognize that the wind slab problem is intertwined with a newly buried and widespread weak layer that remains sensitive to remote triggering. Wind-loaded slopes will have even more weight on weaker layers, and wind-affected areas are likely to have variable snow depths and spots where you can more easily impact these layers. The best—and really only—way to manage this problem is by choosing lower-angled slopes.

    The evidence of a sensitive problem should be clear: Granite Canyon, 25 Short, Wimpys, Broken Branch, South of Teton Village.  

    (1/30/2023)

    This very large avalanche was triggered by parties on Mt. Taylor yesterday. 

     

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    The November 27 layers of facets and crust+facets have become harder to trigger, but the jury is still out on how the additional load of snowfall will play out on these layers.  When persistent weak layers become deeply buried beneath a dense slab, it presents a tricky scenario.  Avalanches become harder to trigger, but the resulting slide would be catastrophic. These weak layers may be more easily impacted by your weight at mid-elevations where the slab is thinner, or in rocky and/or wind-affected areas where there are shallower areas. Observations, since the storm ended, are still fairly limited, and there's a high level of uncertainty with the state of the snowpack in this zone. One thing is for sure—you don't want to tangle with one of these avalanches. Areas with the highest likelihood of triggering this layer are on the southern half of the compass above 8000’. 

    Avoiding terrain where both of these problems overlap will be key this week.

     

    (1/30/2023)

    Natural avalanches on Buck Mountain in the Tetons.

    Photo: Antonioli

Avalanche Discussion

Danger Lessons

The snowfall received from last Thursday through Saturday is the highest 2-day total on record. This information alone should bring you to pause about your terrain choices today, and for the remainder of this week. The balance of evidence and uncertainty is at the forefront in backcountry decision-making processes. Fortunately, we have plenty of evidence pointing towards a sensitive problem that is widespread and capable of producing large and destructive avalanches. We know which flavor of avalanche to expect, and why. 

We can slip into confidence all too easily, without a push in that direction, particularly days after recent snowfall or with colder temperatures. Contextualize all this evidence into your right here, right now decision-making: historic and rapid loading, recent human-triggered avalanche activity, fluxes in temperatures, and settling of new snow into hefty slabs. Choices in terrain should match this evidence, and not our personal history with an area, what someone else skied recently, or anything else that is prone to spring us into a human trap. Grasp the handle of evidence front and center in your context of making decisions on a slope-by-slope basis. The real question remains: Do we as individuals, and as a larger community that models behaviors to others, have the resolve to execute a danger/problem assessment every day, every slope, on our own dime? If not, we trend towards guessing-- a practice that does not lend itself well to repeatability. 

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