Lawinenlagebericht

Togwotee Pass

Bridger-Teton Avalanche Center
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Lawinengefahr

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

Kernpunkte

 Avalanches are most likely on slopes where the wind has built sensitive slabs with recent snowfall, particularly in the upper elevations. Look for evidence of wind such as drifts, stiffened surfaces, or cornices. Larger avalanches involving layers of weak snow buried 1-3 feet beneath the surface are also most likely in steep, wind-affected terrain, but are possible in sheltered terrain as well. Safer conditions can be found on wind-sheltered slopes.

Lawinenprobleme

  • Persistent Slabs

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

    Consistent snowfall is adding gradual load to deeper layers. These persistent weak layers are still showing sensitivity, but are becoming more stubborn as they get buried deeper in the snowpack. This is especially true with the November facets. Surface hoar and near surface facets from early December aren’t buried as deeply and continue to remain sensitive to human triggering. Several recent avalanches have been larger and on deeper layers, which is giving us some bullseye feedback. 

    Significant storms in December built a dense 2-5' thick slab on top of these layers.  In wind-exposed, upper-elevation, and rocky areas, wind and snow over the past several days have continued to add more load to the buried weak layers. In this sort of terrain, shallow spots where you could impact the weak layer are more common. Southerly aspects remain shallower, and you are more likely to impact these layers, but weak snow is not limited to this aspect. 

    (1/1/2023) Recent large natural avalanche on Angle Mountain at Togwotee Pass.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Continued snowfall will produce sensitive wind slabs at upper elevations.  If you find yourself in wind-loaded terrain, you're also in an area where you are most likely to awaken any deeper, weak snow issues. Steep slopes where recent drifts sit atop a shallower snowpack are where you're most likely to get into trouble.

    Additionally, some avalanches (though smaller in size) may occur within the past week's snow due to consistent snowfall paired with changing temperatures. These will likely be 8-12+ inches in depth.

    Yesterday, Alex and I observed several old (and deep) avalanche crowns at Togwotee Pass around Angle Mountain and Breccia Peak. Winds above 8'000 feet were crafting fresh slabs, and plenty of new snow was available for transport. If you're traveling through thicker snow or see cracks around your feet, skis, or machine, you've found a wind slab. Wind-affected areas can be identified by pillowed drifts or dunes, cornices along ridge crests or running down sub-ridges, and/or stiffened snow surfaces. These stiffened snow surfaces may also be buried beneath lighter, fresh snowfall. 

Avalanche Discussion

When dealing with avalanche hazards and problems, it is important to understand the context of thinking in probabilities. Although the rating here just dropped from considerable to moderate in the upper elevations, it is easy to get message fatigue and not really think about how the snow is constantly changing. When snowfall is consistent and gradual, the snowpack may not really show its cards. This puts us, as backcountry users, in a particularly low-feedback scenario. Avalanches occur and get covered up by more snowfall, are blown in by the wind, or happen overnight, and it's important to understand that we see such a small spectrum of what happens in a range on a given day or storm cycle. Even with so many user observations--which are helpful to the community and we are incredibly grateful for--many have a bias toward frequented locations and may be less representative of deeper or less visited areas. Moderate, by definition, means human-triggered avalanches are possible. I find it helpful to think of this possibility in a different context. If I offered to give you a ride in my car on an icy pass but mentioned that I wasn't feeling 100% and it was possible that I may drive off the road or into another car, how would you feel? Would you feel comfortable just hopping in and trusting I would be fine? Or would that possibility raise a few questions and require you to assess me differently?  [Side note-I'm actually a good driver]. 

Our goal is to provide you with more nuance to conditions that may be oversimplified by a given avalanche problem and danger rating. The mere presence of buried persistent weak layers, even when deemed unreactive and not widespread, adds an element of complexity and unpredictability to snowpack assessment. With our current conditions, the places where you could trigger an avalanche on a persistent layer are becoming more and more isolated. But it's definitely not a free-for-all; if you go looking for trouble, you may find it.

 

 

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