Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Sun
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Limite del bosco
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Sotto il limite
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In sintesi

Spring weather is driving a daily rapid warm-up that is impacting and destabilizing the snowpack. It is hard to know exactly how this will play out, things change quickly this time of year. Wet loose, wind slab, cornice fall, and deep persistent slab avalanches are all in play. Choose terrain carefully and be prepared to back off terrain, and out of the mountains, as things heat up.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    Wet loose avalanches are expected today on any slope warmed by the sun. Keep an eye out for changing conditions. Thawing, wet, or slushy surfaces indicate the potential for wet loose avalanches. Snow will quickly change from softened to unstable. Rocks, trees, and cliffs warm especially fast as they capture the sun’s heat and can rapidly destabilize nearby snow. As we transition into a spring snowpack, mountain travel should adjust accordingly. Plan your day so that you are not on or under slopes as they heat up. Heading out and then getting out early becomes an important strategy this time of year. 

    Pinwheels, or rollerballs, are indicators of warming snow surfaces and wet loose avalanche conditions.

    Photo: Noah McCorkel

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–2

    The wind slabs formed by recent weather have likely become harder to trigger in the last 24-hours. Continue to monitor for signs of wind-transported snow; textured or pillowed surfaces, shooting cracks while traveling, and stiff snow are all indicators. Wind slab avalanches still have the potential to step down and trigger larger, destructive deep slabs.

    Cornice Fall: This hazard is becoming more likely as temperatures warm each day. Large cornices have formed throughout the Greys and are being weakened by the daily spring thaw. Cornices should be given a large margin throughout this warming period. Travel on or under cornices is not advised. Be aware that cornices often fail far back.

    (3/14/2024)

    The left flank of a recent avalanche from upper Hunter Creek. 

    Photo: Cameron Galt

  • Deep Persistent Slabs

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

    In much of the Greys forecast zone at middle and upper elevations, weak snow from December is buried up to 5 feet deep. The layer is very stubborn to human or snowmachine triggers in most locations but it continues to produce avalanches with each round of new snow, wind-loading, or cornice fall. These rapid changes in stress to the snowpack appear to be the most likely way to trigger an avalanche but don't overlook the potential to step on or ride over a thin spot which then causes a crack to propagate widely across a slope. Watch for cornices as you travel and evaluate convex slopes and thin, steep rocky, and wind-affected areas carefully. Terrain configuration and wind affect over time matter. Check out recent observations here and here for other examples of this problem.

    The best way to manage this avalanche problem is to build in a large margin for error in your intended route. Increase your safety margin by traveling where the snowpack is deepest, identifying the presence/depth of the weak layer (probing or digging), and avoiding thin, steep, rocky, and wind-affected areas. This problem can be hard to identify and will not show signs of instability like cracking or collapsing. Furthermore, tracks on a slope are not conclusive evidence of stability.

    This is a recent example of an avalanche that was likely triggered by a cornice fall and stepped down to weak layers at the base of the snowpack.

    Photo: Frank Carus

Avalanche Discussion

The Greys River forecasting zone is made up of multiple mountain ranges that have similarities as well as differences in their snowpacks. The Wyoming Range continues to have a thinner snowpack and buried layers of weak snow may be easier to trigger as they sit closer to the surface. The slopes in the Snake River Canyon will likely heat up quickly today by the spring weather we expect. Large cornices have been built throughout the zone and may fail naturally or from the weight of a single skier or rider. 

While there are differences in the various mountain ranges, they do all hold the potential for a variety of different kinds of avalanches today. Deep persistent slab hazard exists throughout the Greys. Cornice falls and wet loose avalanches will become more likely as things heat up each day. Getting out in the spring comes with unique considerations. We often try to time things “just right” to hit softened snow but head home before thawing impacts stability. Pay attention to changing conditions. Note when surfaces start to thaw and use that information to plan future days out. Be prepared to get out of the mountains before you are on or under slopes that are too warm.

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