Bollettino valanghe

Togwotee Pass

Bridger-Teton Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
Senza grado
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It is possible to trigger a large avalanche up to 2 feet thick on steep slopes. Although unlikely, avalanches could break deeper than you expect into older, weak layers close to the ground. Evaluate steep slopes carefully watching for thin spots like rocky outcrops and around wind-affected areas where the weight of a single rider could impact buried weak layers. If you are unsure, seek out lower-angle terrain where you will also find the best riding.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Triggering a large avalanche up to 2 feet thick is possible where weak layers have been buried since the beginning of February. The current slab sits on a variety of weak surfaces, including crusts/facets on solar aspects and facets on shady aspects. This problem could be sensitive to the weight of a single rider or snowmobile. You are most likely to trigger an avalanche on very steep rocky slopes. Specifically, consider where the overlying slab might be thin and where you can more easily impact weak layers below - such as around the margins of wind-loaded slopes. Large triggers like snowmobiles, cornices, and small avalanches in more recent snow will increase the likelihood of triggering a large avalanche. Dig down and investigate layers in the top two feet of the snowpack, but keep in mind that buried weak layers from the January dry period will be as deep as 4 feet in wind-loaded areas and will not show any signs of instability like cracking or collapsing until an avalanche is triggered. Continue to travel safely by going one at a time around steep avalanche terrain and spacing out around terrain traps like creek beds and gullies.

    Additional Discussion: Small wind slabs may form at upper elevations where south winds have transported snow. Carefully evaluate terrain where wind slabs typically form, such as ridgelines, cross-loaded gullies, and leeward slopes. The formation of drifts, cornices, or blowing snow will help you identify where slopes are loading. 

    (2/11/2025) Photo: Bridger-Teton Avalanche Center

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2–3

    Above 9000’ - the base of the snowpack holds weak snow on W - N - E aspects. This snow is buried 5 feet deep on average. Although it's unlikely to trigger an avalanche at this depth, it's not impossible. On February 10th, a rider stepped off their sled, triggering a very large avalanche on Lava Mountain. A deep slab avalanche is most likely where the overlying slab is thin and riders can more easily impact the underlying weak layer. Since these avalanches are difficult to predict, are a low likelihood/ high consequence event, and don't show signs of instability - terrain choice is your best tool. Avoid very steep, convex, rocky, and heavily wind-loaded slopes.

    (2/11/2025)

    The crown of the recent unintentionally-triggered avalanche on the E face of Lava ~10,400'.

    Photo: Bridger-Teton Avalanche Center

Avalanche Discussion

Today we have transitioned the basal facet layer in Togwotee from a persistent slab problem to a deep persistent slab problem. This layer is unlikely to produce an avalanche, but recent evidence has shown that it is still capable of producing very large, unsurvivable avalanches. Our travel advice and management of this problem is similar to the persistent slab problem, but moving forward we will have a better ability to distinguish between the distribution and sensitivity of weak layers within the snowpack. 

If you are uncertain whether a steep slope could avalanche and don’t want to dig to investigate weak layers, consider the consequences if you are on that slope, and it avalanches - I am certain that there are few good outcomes getting caught in a large avalanche or even a small avalanche in a terrain trap.

Please consider submitting an observation HERE. Observations allow everyone to gain a better and more complete understanding of conditions. Thanks!

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