Bulletin d’avalanche

Togwotee Pass

Bridger-Teton Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
Sans niveau
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Avalanche danger will increase throughout the day as temperatures rise well above freezing. Triggering a wet snow avalanche is possible on solar aspects at all elevations. Additionally, weak layers buried deep in the snowpack exist on steep shaded aspects where triggering a large destructive avalanche is unlikely but still possible. Move to lower-angle terrain if you encounter wet unsupportable snow. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Wet snow avalanches are possible today, and the threat of point-release avalanches and larger human-triggered avalanches will increase as temperatures warm. Overnight temperatures fell below freezing at upper elevations allowing the snowpack to refreeze. Snow will reheat quickly with today's forecasted high temperatures and limited cloud coverage. Winds from the southwest may slow the warming process but expect wet snow on solar aspects by mid-morning. Wet avalanches could entrain enough surface snow to carry a person or sled and could trigger a larger slab, especially in previously wind-affected areas. While wet slab avalanches are not likely today, high temperatures and solar input will cause water to start flowing through the snowpack. Due to the unpredictable nature of these avalanches, avoid lingering under steep, sunny, or rocky areas, especially where large cornices have formed above. Consider moving to lower angle, or northerly terrain if you find signs of unstable wet snow such as roller balls, pinwheels, or a mushy unsupportable snowpack. 

    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 yesterday triggered a very large avalanche (D3) that ran to the valley floor.

    (4/4/2024)

    A D1.5 wet loose avalanche. Wet loose avalanches often start at a point, near exposed rocks or trees, and fan out. 

    Photo: Cameron Galt

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    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. Widespread natural avalanches on the weak layers in this zone will require more heating and flowing water. 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

As temperatures warm throughout the day, expect the snowpack structure to become unsupportable. We are entering a period of warming and strong sunshine. Water may start to move through the snowpack bringing wet slab avalanches back onto the radar. While wet slabs are unlikely today, this avalanche problem is known for its unpredictable nature. Therefore, it would be a good idea to minimize your time on steep solar aspects, especially during the heat of the day. Watch for mushy unsupportable snow. If you dig down and find slushy snow or free-flowing water within the snowpack, consider that a red flag and move to lower-angle or more northern terrain. Additionally, slabs could be released with large triggers. Cornices that have formed over the season will become weaker with warmer temperatures. These cornices could release at any time, triggering larger avalanches on slopes below. Identify cornice formations and minimize time spent beneath them. These problems will persist through the weekend as temperatures steadily climb into the beginning of next week. Thankfully, excellent riding may be found on lower-angle slopes when the snowpack softens, or on northern terrain that has seen less warming and sunshine. 

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