Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
4 · Gross
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Conditions are very dangerous and you are likely to trigger a large, 2-4 foot thick avalanche. Natural avalanches reaching the valley floor remain a possibility. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes. Avoid traveling on or below slopes steep enough to avalanche.

Avalanche Danger is greatest in the mountains and drainages above Smiley Creek and in the South Fork of the Boise River drainage, where more snow has fallen. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3

    While the storm has ended and the Avalanche Warning expired, conditions are still very dangerous. Triggering a large, destructive avalanche 2-4 feet thick is likely. Yesterday, skiers near Smiley Creek reported widespread collapsing of the snowpack. Snowmobilers riding in the adjacent Galena Summit & Eastern Mtns zone remotely triggered an avalanche while riding in a flat meadow below (photo above/right). It released 800-1000' above them. These are clear indications that we're nowhere near being out of the woods.

    The weekend storm walloped an early-season snowpack with multiple persistent weak layers. The result was predictable, but impressive nonetheless. An avalanche near the top of Galena Summit closed HWY 75 for 24 hours—as a result, we've received very few observations from this zone. In the Wood River Valley, several houses were hit, the river was temporarily dammed, and Warm Springs Road was blocked. For more details, read the Forecast Discussion below. For more details, read the Forecast Discussion below.

    Conservative terrain choices are essential to staying safe in the backcountry. If you trigger an avalanche, it could be large enough to be unsurvivable. Steering clear of avalanche terrain and areas exposed to steeper slopes above is the only way to avoid this problem.

    ADDITIONAL DISCUSSIONThe recent storm was accompanied by S-SE winds that blew strongly at times. Drifts and slabs that formed in wind-exposed terrain during the storm may remain sensitive. This problem pales in comparison to the persistent slab problem described above. If you trigger a wind slab, it's likely to "step down" into more deeply buried weak layers and produce a much larger avalanche.

    (12/12/2022) Snowmobilers riding in the Boulder Foothills on Monday, Dec 12, remotely triggered this avalanche while riding in a flat meadow below. It released 800-1000' above them. It released from approximately 9300' on a W aspect.

Avalanche Discussion

To keep track of all the avalanche activity produced by the weekend storm, the SAC forecast staff were all wishing we had the latest Intel Core i5 5GHz processor instead of our measly brains. I'm fairly certain all of us saw spinning beach balls and/or crashed and rebooted several times. If you're not a computer nerd, what I'm saying is that a lot happened over the past few days, and much of it came fast and furious.

With today's clearing skies, we'll start to get a better view of the avalanche activity produced by the recent storm. But even with the poor visibility the last few days, an impressive array of avalanches were reported. Many of these reached valley floors and impacted the urban interface. Here's a quick rundown of some of the observed activity: 

  • Yesterday, a skier was caught and carried by an avalanche on Scorpion, an out-of-bounds run near the Warm Springs base of Bald Mountain. Nearby skiers helped extricate him, and he was transported to the hospital to treat unknown injuries. 
  • A very large avalanche occurred in the Warm Springs drainage near Frenchman's Hot Spring (photo). This slide reportedly damaged a vehicle and a structure. Warm Springs Road was blocked by another large avalanche from a path that hasn't slid in recent memory. 
  • Della Mountain west of Hailey avalanched in many locations, with multiple slides running to the valley bottom. One slide blocked and temporarily diverted the Big Wood River (photos and more details here).
  • At least three houses were hit by avalanches around the city of Ketchum.
  • A large natural avalanche was observed just outside of the ski area boundary at Bald Mountain. The crown of this avalanche was 3-4 feet thick (photo).
  • Dozens and dozens of "roof-alanches" were observed. Though relatively small, these can easily be deadly. 
  • Highway 75 near Galena Summit was blocked by an avalanche, but finally re-opened yesterday.
  • A large natural avalanche failed above the East Fork of the Big Wood River around 1 PM on Sunday. The powder cloud came down to the valley floor.

The storm has ended, but the persistent slab problem isn't going away any time soon. The stakes are high—triggering an avalanche is likely, and it could be large enough to be unsurvivable. For the time being, conservative choices are essential and avalanche terrain avoidance is the name of the game.

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