Lawinenlagebericht

Togwotee Pass

Bridger-Teton Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
Keine Stufe
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Kernpunkte

Avalanche danger may rise to Considerable with continued warm temperatures and sunshine. Large wet avalanches may occur naturally or with a human trigger on steep slopes facing the sun.  While unlikely, the potential of triggering a large destructive avalanche on weak snow buried deeply in the snowpack remains, primarily on northern aspects. If you find wet, unsupportable snow, move to lower-angle terrain. 

Lawinenprobleme

  • Wet Slabs

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

    Wet snow avalanches may become likely at Togwotee today. The threat of natural or human-triggered wet avalanches will increase as temperatures warm. Steep, sunny and rocky areas are where these 1-2 foot thick avalanches are most likely to occur.  Overnight temperatures remained above freezing at all elevations overnight. Snow will continue to heat quickly with today's forecasted high temperatures and direct solar input. Overnight winds may have caused a superficial refeeze, but expect wet snow by mid morning on solar aspects. Due to last night's warm temperatures, the melting required to trigger wet slabs may happen quickly with direct sunshine, especially in more wind-sheltered locations. Wet avalanches could trigger a larger slab avalanche, particularly where weak snow is buried deep in the snowpack. Avoid lingering under steep, sunny or rocky areas, especially where cornices have formed overhead. If you see signs of instability, such as roller balls or wet unsupportable snow, move to lower-angled slopes. 

    Cornices have grown large this winter with more snow added in the past week. While cornice collapses are generally unpredictable, they can act as large triggers. Failures are most likely to happen in the heat of the day. A large collapse in the Tetons triggered a very large avalanche (D3) that ran to the valley floor.

    (3/20/2024)

    Wet avalanche debris can often run further than expected. 

    Photo: Cameron Galt

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1.5–2.5

    Triggering a persistent slab avalanche on weak snow buried 2-4 feet deep is unlikely but not out of the question. See the attached picture of the cornice-triggered avalanche in the Tetons for evidence. As temperatures increase through the day, weak snow buried in the snowpack may become more sensitive to triggers. The most probable areas to trigger a persistent slab avalanche includesteep, rocky, and wind-affected slopes on the north half of the compass. These areas contain thin, shallow spots where riders can easily impact weak layers. Shallower snow is also found east of the continental divide and south towards the Gros Ventre Range. Previous tracks on a slope are not an indicator of stability. Use caution in steep terrain and give yourself a wide margin of error on slopes with high consequences or near terrain traps. Move to low-angle terrain to avoid this problem. 

    The last known persistent slab avalanche occurred on 3/16 in Upper Deception Creek. On 3/19, a wet slab avalanche failing on these persistent weak layers occurred on Breccia. More avalanches such as these are possible during spring warm-ups and may span the border between a wet slab and a persistent slab problem. However, both will be equally destructive avalanche types.

    (4/10/2024) Photo: Dan Hays

    This avalanche crown looks about 200m wide, 2-3m thick and took most of the season snowpack with it. It occurred 4/10 on the Wedge at around 10,000',  SSE of Grand Targhee.

Avalanche Discussion

Warm sunny weather will continue to drive change within the snowpack today. Wet slab avalanches are challenging to predict, but today's weather is consistent with the conditions needed for wet slabs. We have layering in the snowpack, overnight temperatures above freezing, and direct solar input. With that in mind, plan your day accordingly. During spring months, starting and ending your day early will help reduce risk. You avoid the heat of the day this way, and therefore peak hazard. If you find yourself in wet unsupportable snow, you've found a red flag. Move away from slopes with similar characteristics. As we transition into the spring months, the difference between persistent slab problems and wet slab problems will become less defined. Both avalanche types are equally destructive, and rapid warming can increase the likelihood of both problem types. Watching for signs of warming will help you avoid both problems.

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