Bulletin d’avalanche

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Danger d’avalanche

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

Points saillants

It remains possible to trigger a wet slab avalanche this morning until cloud cover, wind, light accumulating snowfall  and a refreeze stabilize the snow. Shaded, northerly aspects may be a better option for riding without the risk of wet, slushy or icy surfaces. Evaluate snow, weather and terrain carefully today if you choose to go into avalanche terrain.

Problèmes avalancheux

  • Wet Slabs

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

    Wet slabs continue to be a concern this morning due to warm temperatures overnight and the potential for periods of sunshine this morning. Partial cloud cover in the mountains overnight limited the refreezing that occurred earlier this week so the potential for water flowing through the snowpack remains. Water continues to drain through the snowpack from yesterday's warmth with more flow potentially this morning on solar aspects.  This risk exists primarily around rocky terrain where rocks radiate heat and direct water into the snowpack.  Cloud cover and wind should cool down surfaces and help lock up the snowpack as the day progresses. This avalanche problem is trending towards unlikely today as wind and cloud cover increase. 

    (3/19/2024) This avalanche was triggered by a snowcat pushing snow onto a ski slope Tuesday afternoon. 

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–3

    Weak snow that formed in December persists at the base of the snowpack across the entire Greys River forecast zone. However, the thickness of the hard slabs that overlay this weak snow varies based on geographic location. In the middle and upper elevations of the Salt, Snake River, and deeper portions of the Wyoming Range, these weak layers are buried 3-5+ feet deep making it difficult for a human to impact them. In shallow parts of the forecast zone, such as the far eastern side of the Wyoming Range, these slabs are only 2-3 feet thick making it possible for humans to trigger avalanches on the buried weak layers. Shallow, rocky, and unsupported terrain on the north half of the compass is where this problem has been most active. Keep in mind that a large trigger such as a cornice fall could trigger one of these very large avalanches, even in areas where the snowpack is deep.

    Careful snowpack evaluation is required in the Greys River zone due to variable snow depths. Probing or digging can provide useful information about the depth to the weak layers preserved at the bottom of the snowpack. This evaluation is critical if you are riding in a shallow part of the zone. A total snow depth less than 6 feet (200cm) is a red flag.

    The last reported human triggered avalanche involving deeply buried weak layers occurred on March 9th on the far eastern side of the Wyoming Range.

    (3/19/2024)

    Large avalanche near Gunsight Pass that failed during early March storm on deep persistent weak layers. 10,200' NE aspect.

    Photo: Alex Drinkard

Avalanche Discussion

Wet slab avalanches are notoriously hard to forecast. Not only is the energy balance difficult to measure but snowpack structure and specifically stratigraphy of crusts within the snowpack all play a role in confounding efforts to make any accurate prediction, especially across wide geographic areas. Lacking the fancy instrumentation to measure  the energy balance in the snowpack, one is left with air temperature trends and direct observations, specifically triggers running around in the mountains. Fortunately, or unfortunately depending on your perspective, there aren't alot of triggers to give feedback or confirm or refute stability when conditions turn wet, variable and less than ideal.  Today we are transtioning from a warm, wet snowpack and moving towards a colder, snowier one. Until we arrive there, which should happen in the next couple of days, we are left with icy surfaces, some freewater in the snowpack and challenging conditions in which to find good riding conditions. If you go out in the mountains today, remember that water and heat remain deeper in the snowpack, despite what may be an icy surface right beneath your feet.

If you choose to make today a rest day (suggested option) or otherwise have some free time, public avalanche forecasting operations like ours would love to have your help improving our product. Please take some time to complete the survey below. Similar studies are responsible for what is widely regarding as improvements in public forecast products like the BTAC platform but more research is needed. 

Invitation to participate in the survey: 

The Colorado Avalanche Information Center, the Avalanche Research Program at Simon Fraser University, and the U.S. National Science Foundation National Center for Atmospheric Research are researching how skiers, snowmobilers, snowshoers, ice climbers, and anyone else who travels in the backcountry interpret avalanche forecast information. Part of this research includes a specific survey to better understand how useful avalanche forecast information is for trip planning. 

Completing this survey will take approximately 20 minutes. Thank you for sharing your feedback to help us improve avalanche risk communication. 

Link to the survey: 

https://caic2024.avalancheresearch.ca/en/

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