Boletín de aludes

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Sawtooth Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You're likely to trigger a 2-3 foot thick avalanche on many slopes. Wind-drifted terrain is the most dangerous, but you could also trigger a slide in sheltered areas. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    Triggering a 2-3' thick persistent slab avalanche is likely on many slopes. Chris' video (above/right) exemplifies this problem. Persistent weak layers (sugary facets, surface hoar, or crusts) exist on most aspects and elevations. The weakest facets we've found are on shadier aspects.

    Thick slabs are more common as you climb into terrain that's exposed to the wind. Recently wind-loaded slopes with stiffer snow in the top couple of feet of the snowpack are the most likely to produce large avalanches. You're less likely to trigger a large avalanche on lower-elevation slopes and those more sheltered from the wind.

    Snowpack cracking and collapsing are clear symptoms of an unstable snowpack. Tilt that collapse onto a steep slope, and you're flirting with an avalanche. Collapses can travel large distances releasing avalanches above you or on nearby steep slopes (photo). Wind-loaded areas feel stiffer under your skis or sled and are more supportable. Don't be fooled, the weak snow beneath the slab still exists (video).  

    Unfortunately, avoidance is the only way to effectively manage this problem. Skiing or riding steep terrain is a risky roll of the dice. Recent reports of skier-triggered avalanches, abundant cracking and collapsing, and a widespread poor snowpack structure (dense slab + weak layers) are all the reasons I need to continue to travel conservatively. 

Avalanche Discussion

Yesterday, I rode out Baker Ck and toured up Fox Pk in the Soldier and Wood River Valley Zone. For the most part, I utilized well-traveled snowmobile trails and skin tracks and never felt a single collapse. In my mind, I thought "hmm, this is misleading..." because I knew what to expect as soon as I left the trail or extended a switchback. Sure enough, hopping off my sled to dig a quick handpit revealed an incredibly weak snowpack. I observed this setup over and over again throughout the day. As I skinned to the top of Fox Pk, I wrapped around into undisturbed snow on its SE and E faces, producing collapses every 50' or so. "That's more like it," I thought.

I couldn't shake the thought of how easy it could have been for someone to follow the well-worn path to Fox Pk and decide to ski steep terrain, forgetting or simply ignoring the glaring red flags we're seeing across the forecast area. Over the past week, nearly every observation reported an avalanche, cracking or collapsing.

I wish I could tell you that this problem is substantially improving, but I can't. SAC staff still expect to be able to remotely trigger an avalanche and plan their tours with that possibility in mind. The good news? You can still enjoy a safe day in the mountains if you plan accordingly. The snowpack is fairly supportable in many areas, making for fast, enjoyable turns on lower-angled slopes. At lower elevations near Ketchum, Hailey, and Carey, W-S-SW aspects had very little snow cover prior to the big early December storm. There, the persistent weak layers are less worrisome. 

Special thanks to those sending in all the great observations!  We've received several over the last week. They are a great way to let others know what you're seeing and they improve our forecasts.

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