Bulletin d’avalanche

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

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

Points saillants

Wet avalanches will become increasingly likely as the day heats up and the merciless April sun cooks the snow. Start your day early and be ready to pull the plug and go home early as the snowpack melts and loses strength. Slides that start small may become large and destructive. If your skis, boots, or machine are sinking deeply into wet snow, you've overstayed your welcome. Small dry snow avalanches are possible on shaded slopes in our highest mountains.

Problèmes avalancheux

  • Loose Wet

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

    Skiers and riders reported seeing and triggering many wet loose avalanches this week (photo at right/above). Last night was the second night in a row with mountain temperatures above freezing. The very weak crust at the surface will break down quickly, revealing the wet, unsupportable snowpack underneath. Slides will get larger and become increasingly likely as the day warms up. Today's wet snow avalanches will come in two forms:

    Surficial loose snow avalanches involving the upper 4-12 inches of snow are the most likely type of slides. These will be easy to trigger on very steep slopes where the upper snowpack is wet and will be dribbling down naturally under the influence of the sun and hot temperatures. These types of slides can occur on all aspects, as temperatures are warm enough to melt the snow surface even on shaded slopes. These slides are relatively predictable and manageable, as long as they stay near the surface.

    Gouging loose and wet slab avalanches are less likely, but any such slide would be large and destructive. On many slopes, the snowpack is moist or wet all of the way to the ground. Hot temperatures and intense sun will be rapidly melting the snow surface, pushing more meltwater into the snowpack. As this water works its way down it weakens the entire snowpack. Surficial slides that start small may gouge deeply into wet snow below, entrain lots of debris, and become large and destructive. When meltwater is pooling on top of prominent crusts in the snowpack, wet slab avalanches become possible. We have not seen any large wet slabs out of the current cycle of heat and sun, but the recipe exists in our snowpack.

    Small wet loose avalanches and larger cornices (photo here) are likely to be failing naturally today. In the right terrain, these can produce large avalanches. Pay attention to the terrain above you as well as the terrain you are moving through. Give cornices a wide berth, these mountain gargoyles are dangerous in their own right. 

    ADDITIONAL DISCUSSION - DRY SNOW: If you grin and bear it through all the wet snow, you'll emerge into a slightly more wintery world above ~10,500'. Here, you may trigger small sluffs and thin wind slabs. Neither of these are likely to be large, but both can knock you off your feet. If these slides are running down into wetter snow lower on the slope they will take on a more destructive wet character. 

    (4/6/2024) Debris from a large wet slab that released in Basset Gulch near Baldy. This slide failed on a NNE aspect at 7,000', likely sometime on Thursday or Friday.

Avalanche Discussion

WET, HOT, and HARDER TO PREDICT

Last night was the second night in a row that mountain temperatures remained above freezing (I put a temp graph in the gallery below, the dashed line is 32 F). Cloud cover decreased after midnight, allowing the snowpack to radiate out some of its energy to the dark sky (link to an interesting blog post about this phenomenon). This process helped to form a thin crust on the surface of the snow, despite above freezing temperatures. Don't expect this crust to last long. Underneath, you'll find a wet snowpack that can produce wet snow avalanches.

The past week brought some beautiful spring riding and skiing conditions to our mountains. The corn was peeling, the windows were wide open, and there was excellent, cold, dry powder waiting for you if you went looking for it. I hope that you were able to get out and savor some of that flavor, as conditions have now deteriorated significantly. Any window of corn skiing that you find this morning will be very narrow. On shaded slopes, the snow on all but the highest peaks has undergone some significant melting. Even if you are finding a few good turns up high, expect conditions to get progressively worse as you descend. 

All of the wet snow avalanches that we have observed in the past week have been relatively small, predictable, and manageable. As the snowpack continues to melt and weaken, the trend in avalanche activity will be toward larger, much less predictable, and much less manageable avalanches. Instead of small, surficial avalanches, you may begin to encounter wet snow slides that gouge deeply into the snowpack and entrain large amounts of debris. Or even worse, large, very dense slabs of water-saturated snow that fail as destructive wet slab avalanches. Predicting the onset of more destructive wet snow cycles is a crapshoot at best.

So what can you do about all this? Unfortunately, I don't have a very satisfactory answer for you there. Start your day early and plan to be out of the mountains early. Head into the mountains with the expectation that you might not get to do any of the things that you were planning on. Our snowpack will need at least a solid refreeze or two to come back into safer, more favorable conditions. Remember to have an exit in mind if/when things get nasty out there; the terrain you traveled through/underneath on your way in will be more dangerous on your way out. 

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