Bulletin d’avalanche

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Wed
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 7 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Steady winds and fresh snow from the past few days are creating sensitive slabs. These new slabs are also adding stress to the weak snow buried deeper in the snowpack. You’re most likely to encounter unstable snow on upper elevation slopes with wind-drifted snow, but sheltered slopes demand your respect as well. Cautious route-finding and conservative decision-making are essential.

Problèmes avalancheux

  • Persistent Slabs

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

    Long lasting layers of weak snow are the name of the game this year. The character of these weak layers varies by aspect and elevation, but you can find them just about everywhere you look. The most widespread layer is a stripe of surface hoar that can be found in the lower to middle portion of the snowpack. This surface hoar has produced most of the human-triggered avalanches that have been reported to us this year. In addition, weak snow near the ground exists on many middle and upper elevation slopes. 

    Persistent weak layers present a complex and frustrating problem for backcountry travelers. They can continue to produce avalanches many weeks after they are buried and they provide fewer and fewer obvious signs of instability as the days without a major loading event pass. They can break wider than you might expect and may be triggered remotely, from gentle terrain adjacent to steeper slopes. Read about my thoughts on how I deal with this type of problem in my personal travels in the Forecast Discussion section found below.

  • Wind Slabs

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

    Continuing snowfall is providing ammunition for the wind. Although it has only been snowing a few inches each day, moderate winds are great at picking up this new snow and depositing it as slabs. Yesterday, as I traveled in the southern Sawtooths, I found fresh drifts up to 1 foot thick in upper elevation terrain. I avoided these slabs where I found them in terrain steep enough to produce an avalanche. 

    We picked up a few more inches of snow overnight and will see another few inches fall today. The wind will continue to build fresh slabs out of this snow and triggering one of these slabs is likely again today. These slabs pose a hazard in their own right, but are also adding stress to the weak snow buried deeper in our snowpack

Avalanche Discussion

We are back to that point where we are talking about likelihood and consequences. I understand, for a lot of you it isn’t the most exciting topic. But humor me here, I think it's worth your time. Take a minute, pour a bit more coffee, and follow me through this thought exercise:

What is the likelihood that you are traveling on a slope with buried weak snow? That’s pretty simple this year - it's very likely. What are the consequences of traveling on such a slope? Well, if you are avoiding avalanche terrain, there aren’t any negative consequences. However, if you are in avalanche terrain, the consequences of triggering and being caught in a slide would be quite high. Continued snowfall and wind loading are creating an increasingly thick slab on top of the weak snow underneath. As the slab grows its potential destructive power increases.

But here’s where it gets tricky: What is the likelihood that you might trigger an avalanche on a buried weak layer if you are in avalanche terrain? Well...it’s possible. There are plenty of places where you might trigger a slide and plenty of places where you might not. As I skied yesterday with a friend visiting from out of town I explained this problem to him. I pointed out steep, enticing slopes covered in fresh, soft snow that would have undoubtedly provided us with some fantastic skiing. But we didn’t do anything more than daydream about them. Didn’t even think about it. We avoided avalanche terrain with buried weak layers; not because we thought triggering a slide was likely, but because we knew it was possible.

We skied great snow in low angle terrain, free from the hazards posed by our persistent weak layers. For me personally, the overriding goal is to come home safely at the end of each day. After all, I can’t go skiing tomorrow if I don’t make it out of the mountains tonight.

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