Lawinenlagebericht

Togwotee Pass

Bridger-Teton Avalanche Center
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Lawinengefahr

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

Kernpunkte

Recent snowfall and wind are creating dangerous avalanche conditions at middle and upper elevations.  The hazard is greatest in wind-loaded terrain but exists on sheltered slopes too. You’re most likely to trigger a slab avalanche in freshly formed wind drifts that are 1-3 feet thick. Avalanches may be triggered remotely — from above, below, and to the sides of slopes. Today, avoiding avalanche hazard requires you to pay close attention to the terrain you are traveling in and to exercise conservative route-finding.

Lawinenprobleme

  • Wind Slabs

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

    Intense periods of snowfall and wind today will stress a buried interface in the upper portion of the snowpack that will likely produce avalanches. Winds have played a significant role in the slab formation portion of the avalanche equation in the past week. The possibility of triggering one of the slabs will be likely today, particularly in heavily loaded upper-elevation and middle-elevation terrain with cross-loaded features. These slabs are also adding stress to the weak snow described below that is buried deeper in the snowpack.

    (12/20/2022)

    New snow is being crafted into sensitive slabs, many of which are sitting atop shallowly buried persistent weak layers as well as other weak layers deeper in the snowpack. 

    Photo: Antonioli

  • Persistent Slabs

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

    New snow and strong winds will stress persistent weak layers buried 3+ feet deep. The sensitivity of some of these deeper layers has decreased over time, but consistent winds and new snowfall will test that reactivity. These layers have remained active primarily on the south and east aspects. Remember that with persistent weak layers triggering avalanches remotely — from above, below, and to the sides of slopes, is a real possibility.  If we go back to the basics, we have persistent weak layers that are getting loaded with new and windblown snow. It is likely some of these layers will hit a breaking point in the coming days as new snow continues to add up. Conservative travel will be the name of the game. 

    (12/19/2022)

    Large natural avalanche on the E face of Static Peak

    Photo: Gavin Hess

Avalanche Discussion

Did someone mention the "w" word? Oh, this wind. This storm marks a significant shift in winter's temperament. We have yet to experience a storm cycle with the amount of wind and snow working in unison, and an additional hazard on the table will be the utterly frigid temperatures moving in this afternoon and into tomorrow. One thing we do know is that natural and human-triggered avalanches will become increasingly common as this storm progresses, likely breaking in one of three ways:

  1. We'll likely see some mid-storm instabilities or slides breaking on the previous snow surface. These slides will likely be on the smaller side and issues will be short-lived.
  2. Triggering a larger avalanche will be most likely on weak layers in the top 1-3 feet of the snowpack that formed between clearings of snowfall over the past week and a half. These newer layers are largely untested, and it will remain difficult to predict their behavior with the forecasted snowfall. 
  3. While less likely, the added load will make it possible to trigger deeper, older layers of faceted snow. Especially in areas with a deeper snowpack, these layers have been showing some signs of improvement, but trajectories remain unclear. These avalanches would be very dangerous, breaking 2-4 feet deep. As the new snow piles up, the chances of infrequent but larger avalanches will increase.

Complex, overlapping patterns of weak snow are very difficult to deal with. The easiest solution is to exercise conservative route-finding and decision-making in your backcountry travels. I know, that’s not what you want to hear.  In the Tetons, the persistent weak layers we've been talking about all winter are becoming deeply buried. The surface hoar and crust+facet combos from early in the winter are now buried beneath 3-4 feet of snow. In Togwotee and the Greys River, the thinner and poorer snowpack structure is just waiting for a slab (happening now). Additionally, newer weak layers that formed prior to this storm are now 1.5-2 feet deep. All of our areas have one thing in common. Even if it comes in different forms, there's a high degree of uncertainty in how each snowpack will react to the storm cycle we're experiencing. Uncertainty means building more margin for error in our terrain choices. I usually find the best approach to said uncertainty is to enjoy some fantastic low-angle powder riding with friends, and see what shakes out.

 

 

 

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