Boletín de aludes

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Peligro de aludes

Mon
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You are most likely to trigger an avalanche on very steep slopes at upper elevations—especially those affected by the wind.  Triggering a large, destructive avalanche breaking deeper in the snowpack is unlikely but cannot be ruled out entirely. Safer conditions—and the best skiing and riding—can be found on gentler slopes sheltered from the wind.

Problemas de aludes

  • Deep Persistent Slabs

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

    Weak October snow is buried 4-6+' deep on most shady middle and upper elevation slopes. Some sunnier, upper elevation aspects have this layer too. The recent storm event just added a huge load to this weak layer, especially on wind-loaded slopes. Yesterday's observations in this zone did not reveal any slides breaking deeply into the old October snow—a hopeful sign that this layer is becoming less of a concern. Also, in much of this zone, the weak layer is so deeply buried that it's very difficult to impact with our weight.

    I suspect you'd have to go looking for trouble to trigger a deep slab avalanche—but I wouldn't recommend that, since the consequences would be disastrous. Where might it still be possible to trigger a deep slab? I would still be leery of very steep (>35 degrees), rocky, wind-affected slopes at upper elevations and in alpine terrain. 

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Last week's storm dropped 50-50" (!!) of new snow in this zone, accompanied by strong winds. Clearing skies yesterday revealed numerous natural avalanches, the majority of which ran on wind-loaded slopes—see the Media Gallery for some examples. 

    Even though the storm has ended, wind-loaded terrain presents two lingering problems. The first is that while wind slabs (like this one) are becoming less sensitive, there are likely a few out there that you could still trigger. The second problem is that wind-affected slopes have more recent loading and a stiffer slab sitting atop buried weak layers (see Additional Discussion below and Problem #2).

    If someone were to trigger a slide today, it would most likely occur in wind-loaded terrain. For that reason, the best approach will be to avoid steep slopes where you find evidence of wind loading such as drifted, pillowed areas,  or feel denser/stiffer snow beneath your board(s) or sled.

    ADDITIONAL DISCUSSIONYesterday's pattern of natural avalanche activity points to a probable crust/facet layer on steep (>35 degrees) slopes that face SE-S-SW. Sun Valley Heli Ski noted multiple slides on sunny aspects (photo above/right), and a similar pattern was observed in the Galena Summit & Eastern Mtns zone (Galena Peak, Pole Creek). Until we have better information on this weak layer, most of us will be avoiding steep, southerly-facing slopes—especially those affected by the wind.

    (1/8/2022) Multiple natural avalanches in wind loaded terrain in the Western Smokys. These ran on SE aspects and likely failed on facet/crust layer that exists at the interface between the recent storm snow and the old snow surface. Photo: Sun Valley Heli Ski

Avalanche Discussion

A BRAVE NEW WORLDLast week's multi-day storm cycle dropped 12-50" of new snow across our area, with the Western Smokys, Smoky Crest, Sawtooths, and Banner hit the hardest. Although this storm didn't change the game as much in the Wood River Valley where less snow fell, many other portions of the forecast area are dramatically different. It's time to take stock and make sense of this new world. Yesterday's clearing skies gave us a first glimpse at the pattern of avalanche activity, but we look forward to more "boots on the ground" observations in the coming days. Let's consider what we do and don't know.

Observations so far (knowns):

  • Numerous storm/wind-related avalanches occurred—not surprisingly given the massive snowfall, intense precip rates, and strong winds. 
  • Enough avalanches occurred on southerly aspects (Galena Peak, Boulders, Pole Creek, Western Smokys) to conclude a pattern exists. These slides likely failed on a crust/facet layer that was the old snow surface prior to the storm.
  • Few observed avalanches broke on the deeper October snow—at least from what we've seen so far. But here's a photo of one that did near Titus Ridge.

Observations needed (unknowns):

  • Is the crust/facet layer on steep, sunny slopes still sensitive or has it "done its thing"?
  • Will additional observations of avalanche activity show more slides that broke in October snow or reveal new patterns?
  • How deeply is the October snow buried? Where is it still a concern?

Until we get a better handle on our brave new world and the "knowns" list is longer than the "unknowns", most of us will be sticking to conservative terrain and embracing a wait-and-see attitude.

Be sure to catch up on last week's conditions in Chris' latest Weekend Update.

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