Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The chance of triggering an avalanche is greatest in the western portion of this zone (Dollarhide Summit to the Soldier Mountains) where much more snow has fallen in recent days. Avoid steep terrain where the wind has formed soft or hard drifts to minimize the chance of being caught in an avalanche. Slopes with soft snow on the surface are much less likely to produce slides. Avalanches can be triggered remotely—from below, above, and to the sides of steeper terrain.

Lawinenprobleme

  • Persistent Slabs

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

    The weak snow buried near the ground continues to be the primary avalanche concern in this zone. While encountering a wind slab (Problem #2 below) is more likely in the western part of this zone, any wind slab you trigger has a chance of "stepping-down" to the weak snow near the ground. Some recent human-triggered and natural persistent slab avalanche activity:

    • Saturday, a rider between Wells and Dollarhide Summits triggered an avalanche on a steep, heavily wind-loaded slope (photo at right).
    • Saturday, a skier on Titus Ridge intentionally triggered a large avalanche. The slide initiated as a stiff wind slab that formed during last week's wind event and then "stepped down" to the December weak layer. Photos and more details are available here. Ben investigated this event (video).
    • Sunday, Sun Valley Heli reported seeing a recent large, natural avalanche that failed near the crest of the Smoky Mtns north of Dollarhide near Baker Ck divide, likely involving this weak snow (photo here).
    • An observer reported fairly recent natural avalanche activity in the Pioneer Mtns west of Grays Peak.

    The depth of the snowpack is highly variable in this zone. In areas where the snowpack is less than about 4 feet deep, the weak layer is much more "accessible" to a skier or rider. This makes triggering slides easier. Strong NW winds over much of the past 10 days have scoured many slopes (bringing the weak layer closer to the surface) and deposited hard slabs on others (adding weight to the weak layer).

    So what sort of areas should you be most worried about right now? The avalanches described above share some characteristics:

    • Slopes steeper than about 35 degrees
    • Wind-loaded terrain
    • Rocky slopes with a thinner snowpack

     This is exactly the type of terrain where you are most likely to encounter this problem today. Recent snowfall has hidden signs of wind events in places, making it more difficult to tell when you're on previously wind-loaded slopes. This fact has made many experienced skiers and riders think twice about entering consequential avalanche terrain, despite the gradually decreasing danger. 

    (2/12/2021) This avalanche was triggered by a rider NE of Wells Summit in the Soldier & Wood River Valley zone. The slide broke around 40' wide and carried the rider about 100 yards. A section of the cornice also released in the slide.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Soldier Mtn Cat Ski staff triggered wind slab and storm slab avalanches in very steep terrain in recent days. They report the slides are running on the hard, wind-hammered surface beneath the recent snowfall. These relatively small slides can have big consequences if they carry you through rocky, treed terrain or push you down into a terrain trap like a gully or a creek bed.

    From an avalanche danger perspective, the larger concern is still the additional loading on the persistent weak layers described in Problem 1. Small wind slab avalanches can be great triggers for more deeply buried weak layers. Any avalanche that steps down to these persistent weak layers will be large and destructive. 

     

Avalanche Discussion

Naps, Hibernation, and Dormancy

The persistent weak layers that produced extensive natural and human-triggered avalanche activity in December and January are finally showing signs of going to sleep. Unfortunately, they aren’t “out cold” yet; they appear to be stuck in limbo.

Think back to a time when you were listening to a boring teacher or professor’s lecture on an early morning when you didn’t get enough sleep the night before. The drone of the speaker’s voice continues, you are not interested, and your head begins to bob and then snap back up as you fight the urge to fall asleep. This is how our persistent weak layers are currently behaving.

When you were falling asleep in class, someone gently touching your shoulder may or may not have been enough to get your attention; this reaction (or lack thereof) is akin to the past several days of low-density snowfall falling on many slopes. However, what if your instructor poked you hard in the ribs with a pencil? You’d instantly snap out of your partial-sleep mode and be more than a little peeved, much like our weak layers on slopes where the wind is rapidly forming stiff drifts and wind slabs, or where small loose snow avalanches are running downhill.

Until it stops snowing and blowing for an extended time, I expect the persistent weak layers on some slopes to be susceptible to a pencil poke in the ribs. The difficulty lies in:

  • Which slopes are nodding off to sleep, and which slopes are “out cold”?
  • How hard is it to poke the weak layers on the slopes where they are still nodding off to sleep? How deep is the weak layer buried?
  • If I wake one of the sleepy students/weak layers up, will it be a meek 80-pound student who tells me off or a 280-pound behemoth who gives me a royal beatdown?

Our snowpack has become quite complex in the past 3 weeks, and it's nearly impossible to answer those questions on a slope-scale unless you’re an experienced professional studying and sampling the same slide paths day in and day out. As most of us don’t have either the luxury or experience to do so, we are forced to travel a little more conservatively than we’d like to give ourselves a healthy safety margin. As always, I encourage you to think about the consequences of triggering a sizable avalanche before committing to riding or skiing large avalanche paths.  

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