Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 7 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering a large avalanche is unlikely.  Unstable slopes are becoming few and far between, but triggering a 1-3 foot thick avalanche may be possible on very steep, wind-affected slopes at upper elevations. A smaller problem—but one that may be more likely—is fresh wind drifting along high ridges and in exposed terrain.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    Triggering a 1-3 foot thick persistent slab avalanche has become unlikely. The weak layers we've struggled with all winter have not gone away, but the last part of January has given them the breather they've needed to become less reactive to the weight of a skier or rider. 

    Are there still slopes where it remains possible to trigger these layers? Probably, but it would likely take a dose of bad luck to find them. Ben was in the White Clouds yesterday where he witnessed some of this bad luck that fortunately turned to good luck. Riders in lower angled terrain collapsed the snowpack, causing a large alpine slope above them to crack, shift—and stop.  In his snowpit, he found especially weak early-season snow near the ground beneath a 4-foot thick slab of snow.

    This incident is a good reminder to keep these weak layers in mind and not completely write them off. While the chances are small, there's a lingering possibility of triggering a large persistent slab avalanche—primarily on upper elevation and alpine, wind-loaded terrain steeper than about 35 degrees.

    ADDITIONAL DISCUSSIONWesterly winds blew at moderate to strong speeds all day yesterday and continued through last night. Snow professionals on Galena Summit yesterday found small but sensitive wind drifts. There is less loose snow to be blown around in our southern mountains, and I would expect wind slabs to be small and isolated. Still, keep your eyes open and use extra caution on slopes that appear to be recently drifted.

Avalanche Discussion

With much of the forecast area trending towards Low avalanche danger, this is a nerve-wracking time to be an avalanche forecaster. This rings especially true with widespread persistent weak layers in the snowpack. Decreasing danger usually leads to more folks riding in steep terrain, which means more people testing your theory of the snowpack stability.

Our theory is that the persistent weak layers have had some time to adjust to the load from the first part of January. Especially in our northern and western mountains, they are buried deeply enough to be difficult to trigger. The weak layers aren't gone, they're just trending towards what we call dormancy and we probably haven't seen the last of them. The last slopes to stabilize in this scenario are usually the "baddest of the bad"—upper elevation/alpine, rocky, wind-loaded terrain steeper than 35 degrees. It would still take some bad luck to trigger an avalanche in these areas, but it's certainly not outside the realm of possibility. Ben's observation from yesterday—described in the persistent slab problem discussion above—provides a counterpoint to the otherwise improving picture of snowpack stability.

The danger scale is a very general description of the overall avalanche conditions. If you've read this far, you likely know that there are more subtleties and nuances to the avalanche danger than can be summed up by one word. As the avalanche danger continues to drop, we hope folks will keep in mind the weak layers under your boards or sled—even if they lie dormant for the moment. If forced to choose between Low danger with persistent weak layers, and Low danger without, I'd choose without each and every time.

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