Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Dangerous avalanche conditions exist today. Natural activity is possible and rider triggered avalanches are likely in steep terrain on all aspects and all elevations. These avalanches could be large and propagate long distances across slopes. Avoid traveling in, near, or under avalanche terrain today.

Problemi valanghivi

  • Persistent Slabs

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

    Snowmobilers and skiers can trigger large hard slab avalanches failing on very weak snow that formed during December. In the middle and upper elevations, avalanches could break 2 to 4 feet deep. Below 7,500’ slab depths will be in the 1 to 2 foot range. Avalanches continue to be triggered on all aspects (shaded and sunny) at all elevations. Slabs could be triggered from a distance, by the first rider, or even wait until the last person in your group is riding the slope to release. Avalanches have the potential to propagate long distances, including entire slopes. Because of this, avoid terrain that is connected to avalanche paths and give runout zones a wide margin. This also means being aware of the terrain that is above you, as remote triggering is possible. Typical safe zones should be reconsidered when traveling below steep terrain. This includes terrain traps such as steep cutbanks and gullies. For the time being, sticking to low angle terrain with little consequence is the best way to mitigate this problem.

    Additional Discussion: Rain on Snow

    Areas below 7,000’ saw significant rain on snow yesterday. Overnight temperatures in the valleys barely dipped below freezing. Be extra cautious of low elevation slopes if temperatures warm significantly today, as the recent rain and lack of a solid freeze could make natural activity more likely.

    Remotely triggered persistent slab avalanche in Squaw Creek. NE aspect 8900' 

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3.5

    Weak snow formed during a dry period in November persists at the base of the snowpack. This layer is now buried about 5 to 6 feet deep in the Salt River, Snake River, and western portions of the Wyoming Range. It is at its weakest on the north half of the compass. Recent loading and warm temperatures are keeping this weak layer on the radar. These very large avalanches are most likely to occur when an avalanche triggered in the most recent snow steps down to weak old snow. Any avalanche involving the entire snowpack will be destructive and likely unsurvivable. 

    Areas in the eastern Wyoming Range, Hoback Canyon, and Gros Ventre Mountains lacked significant snowfall prior to the storm cycle beginning January 4th. In these locations, the new snow has fallen on a snowpack that was primarily made up of weak, sugary snow. Deep slab events are not likely in these locations due to the shallower snowpack.

    (1/16/2024)

    This avalanche failed much larger than it did a few weeks ago. The crown depth indicates that it involved the deeper weak layers from November. 

Avalanche Discussion

A widespread, well connected, and very weak layer of snow that formed during a month-long dry period in December has been overloaded by nearly 7 feet of snow with over 8 inches of snow water equivalent (a huge amount of weight) since January 4th. This loading combined with notably warm temperatures over the past two days has made for dangerous avalanche conditions. Natural activity was reported yesterday in Prater and Green canyons with some slides running through the trees and impacting the trail. Cracking and collapsing continue to be reported across the Greys forecast area. These are obvious signs that the snowpack is unstable and sensitive to human triggers. However, as we move away from last week's big storm, it is important to note that you may not experience any signs of instability. This does not mean that it is safe to ride avalanche terrain. Triggering a large, destructive avalanche may be the first sign of instability that you experience. This is especially true at the upper elevations where snow depths are deeper making it slightly harder to impact the weak snow from December. Conservative decision making is warranted given the size and wide propagating nature of the avalanches that are currently being observed. Give yourself a wide margin today to allow for surprises.

An observation of an avalanche in the Willow Creek drainage that caught and carried a rider last week was recently submitted. The avalanche was 2-3' deep and propagated about 200' feet across the slope. The observation can be found here. Thank you for submitting your observations. They make a difference!

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