Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
4 · Gross
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

The avalanche danger will increase through the day, reaching HIGH at upper elevations in the Soldier Mountains. New and wind-drifted snow are creating touchy wind slabs and adding weight to buried weak layers. Avalanche conditions will be most dangerous on slopes with windblown snow, but it's also possible to trigger a slide breaking 2-3 feet deep on steep, sheltered slopes.  It will be a good day to stick to lower slope angles and avoid wind-loaded terrain—especially in the Soldiers.

Lawinenprobleme

  • Persistent Slabs

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

    We have begun an extended storm cycle that will add significant weight to buried persistent weak layers—especially in the Soldier Mountains where significantly more snow is forecast. Two factors prevent this from being a simple, slam-dunk case where I can tell you exactly what will happen and when. The first is that the new snow load will be added gradually. The second is that we have a complex and variable snowpack with a number of buried weak layers (see video). As new snow piles up through the day, triggering an avalanche will be most likely on weak layers within the top 1-3 feet of the snowpack or on yesterday's snow surface. It will also become possible to trigger deeper, older layers of surface hoar and depth hoar, resulting in a dangerously large avalanche breaking 2-3 feet deep. 

    It's not entirely clear how these buried weak layers will respond to the slow loading, and how much new snow it will take before we start seeing natural and triggered avalanches. When there's uncertainty, I always go back to the basics: we have persistent weak layers, and they are getting loaded with new and windblown snow. When you look at it that way, it's clear that the avalanche danger is on the rise, and we need to scale back our terrain choices by choosing lower angled slopes.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1–2

    While there is some uncertainty surrounding the persistent slab problem, the wind slab problem is cut-and-dry: new snow + wind = dangerous avalanche conditions. The new snow is low density and will be easily transported by today's moderate to strong westerly winds. Expect to find touchy wind slabs in upper elevation terrain, and possibly on exposed mid-elevation slopes.  These wind slabs will be dangerous on their own and are also adding more weight to the persistent weak layers described above. Avoid any slope where you find evidence of fresh wind drifting.

Avalanche Discussion

Today marks a significant shift in this winter's weather. While we've been light on snowfall so far this season, an extended storm cycle that begins this weekend finally breaks this dry pattern. Below-average snowfall in the early season typically produces exceptional weak layers, and that has certainly been the case this year. And now the time has arrived where we will begin to test this season's snowpack. It's not perfectly clear how our aging weak layers will respond to the slow but constant loading over the coming days. But we do know that natural and human-triggered avalanches will become increasingly common, likely breaking in one of three ways:

  1. We'll likely see some mid-storm instabilities or slides breaking on yesterday's snow surface. These slides will be on the smaller side, and these issues will be short-lived.
  2. Triggering a larger avalanche will be most likely on weak layers in the top 1-3 feet of the snowpack that formed since New Years. These newer layers are largely "unproven", making it more difficult to predict their behavior with the forecasted snowfall. 
  3. While less likely, the added load will make it possible to trigger deeper, older layers of surface hoar and depth hoar. Especially in areas with a deeper snowpack, these layers have been showing some sign of improvement and it's not clear what they got left in them. These avalanches would be very dangerous, breaking 2-4 feet deep. As the new snow adds up over the coming days, the chances of infrequent but very large "rogue" avalanches will increase.

While there is some uncertainty with how our snowpack will react to the impending storm cycle, one thing is clear: the avalanche danger is on the rise, and we need to start traveling more cautiously in the backcountry. This means dialing back slope angles, paying attention to the consequences of going for a ride, and avoiding all wind loaded terrain. In our zones that receive the most snow, that will likely trend towards complete avalanche terrain avoidance in the coming days.

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