Bulletin d’avalanche

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You are most likely to trigger an avalanche in wind-affected terrain, where fresh drifts are adding weight to buried weak layers. Look for evidence of wind such as drifts, stiffened surfaces, or cornices that indicate the wind has been at work. Wind slabs may step down to deeper weak layers, producing very large and destructive avalanches. Safer conditions and better skiing and riding can be found on wind-sheltered slopes.

The Avalanche Danger will increase after sunset as an intense storm impacts the region. 

Problèmes avalancheux

  • Persistent Slabs

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

    A mix of facets and crusts leftover from October snowfall make up the base of the snowpack on most middle and upper elevation slopes. This layer is at its weakest on the shaded (N) side of the compass but old snow exists on upper elevation slopes that face the sun as well. The problem is more common in the deeper snowpack areas of this zone, such as the Dollarhide Summit area and the Soldiers, but it exists in the mountains above the Wood River Valley as well. Yesterday, I observed the crown of an avalanche that broke over 500' wide just 5 miles east of Sun Valley (photo at right/above).

    Yesterday, the professionals at Sun Vally Heli Ski experienced a large collapse to the west of this Zone when they landed their helicopter in a safe location and collapsed this layer of weak snow. Public observers traveling in the Galena Summit area have also reported triggering large collapses involving this weak snow in recent days. In steeper terrain these collapses are avalanches. 

    There are two things that make it somewhat less likely to trigger an avalanche on this layer today: the weak layer is buried beneath a very dense slab of snow, and we have not had major precipitation for almost a week. The weak snow is getting a bit of time to adjust to the slab on top of it and that same slab is making it hard for us to impact the weak layer with our weight. But, there is a huge divide between harder to trigger and impossible to trigger. Read the Forecast Discussion below.

    (1/2/2022) This large persistent slab avalanche was observed above Corral Creek, near Johnstone Peak. It failed on a N/NW facing slope at 8,600'. The terrain and trees below the crown limited its size, but the crown is over 500' wide.

  • Wind Slabs

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

    The past three days brought us a healthy dose of erratic, gusty winds blowing out of the NW. Winds shifted yesterday and have been blowing at moderate speeds with strong gusts from out of the S/SW for over 12 hours now. Both bouts of wind built stiff, hard slabs in upper and middle elevation terrain that is exposed to the wind. These slabs present a hazard in their own right and are adding weight and stiffness to the slab overlying the weak snow described above.  In addition to the weak snow at the base of the snowpack, there are also irregularly distributed layers of weak snow in the upper snowpack. I've been out hunting for these this past week and have found them in some places and not others. Watch these videos to find out more: Boulder Mountain weak snow, Stanley Foothills weak snow. Wind slabs that fail on this weak snow will be larger and will break wider than you might expect.

    Small natural wind slabs were observed on Friday by the Soldier Mountain Ski Patrol (photo at right/above). On each of the past two days, I observed wind slab avalanches that failed recently. One in the Smokys (photo here) and one in the Boulders (photo here). Triggering similar slabs will be possible again today. Look for stiffened snow surfaces and textures like ripples that help to identify wind-affected areas. You will find much better skiing and riding conditions in terrain that has been sheltered from the effects of the wind. You'll also be less likely to trigger an avalanche in this terrain. Win-win.

    (12/31/2021) On Friday, NW winds were actively loading slopes - especially in the southern portion of the forecast area. This small wind slab in the Soldiers occurred naturally as a result. Photo: Soldier Mtn Ski Patrol

Avalanche Discussion

THE LION'S DEN

Here is a hypothetical scenario to ponder: If you were forced to entire the den of a lion, would you rather the lion be hungry and angry or well-fed and drowsy? It is a fairly easy choice, if those are your only two options. Give me that sleepy lion any day. But what if I told you that you had three options: hungry lion, sleepy lion, and no lion at all. Well, now we've gone from an easy choice to a no-brainer. We have an ugly layer of weak snow near the base of our snowpack, a lion of the snow. The last significant precipitation in our area was recorded on December 27th, with some dribs and drabs of light snowfall in the time since. This period of rest has helped the weak snow adjust to the load that sits on top of it, which decreases the likelihood of triggering an avalanche involving this weak snow. Decreases, not eliminates.

You can significantly decrease your risk of being caught on the wrong side of a lion today but choosing to avoid the terrain where the lion lives. For us that means avoiding terrain where the wind has been at work building drifts and stiffening the snow surface and where terrain where remnant snowfall from October makes up the base of the snowpack. You may find yourself thinking, "why is he talking about avoiding avalanche terrain if the danger is only MODERATE?" That's a fair question. If I told you that it was possible you were about to get in a car accident would you make sure your seat belt was on and pay close attention to the road? If I told you you were walking through a lion's den would you try to walk as quietly as you could? If I told you a lightning storm was possible would you seek out lower elevation, less exposed terrain?

It is important to recognize that if you enter avalanche terrain where this snow exists you are simply rolling the dice. Maybe the dice has 100 sides and only a handful of those numbers end up with the unacceptable outcome of triggering a massive avalanche. But not triggering a slide doesn't mean you weren't playing the game. Take an honest, realistic look at the choices you are making in the mountains. We don't learn anything if we just pretend that the danger isn't real.

Régions couvertes