Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

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

Kernpunkte

It remains possible to trigger a large, 2-3 foot thick slab avalanche. Buried weak layers were loaded by last week's snowfall and wind, and will be kept on edge by today's sun and warming. To reduce your risk, choose gentler slopes and avoid terrain where avalanches are more likely: slopes with evidence of wind drifted snow and those that face the sun.

Lawinenprobleme

  • Persistent Slabs

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

    Last week's snowfall and wind added a significant amount of new load to the snowpack, and our persistent weak layers are now buried 2-3+ feet deep in this area. While less natural activity occurred in this zone compared to further north, several significant slides were observed—including a large one on Titus Peak. 

    The lack of snowfall and significant wind the last few days have provided our snowpack a much-needed breather. However, we're about to poke one last sharp stick in the eye of the persistent slab problem. Today will be by far the warmest and sunniest day since the start of the January 10th storm cycle. To reduce the likelihood of triggering a persistent slab avalanche today, I'd recommend three things:

    1. Choose moderate slopes with low consequences. With a persistent slab problem, this is our primary line of defense.
    2. Avoid slopes with evidence of recent or past wind drifting. Wind loading may have created a dense slab atop the weak layers.
    3. Avoid slopes that are facing the sun today. The warming temps and sunshine may be adding more stress to buried weak layers.

    ADDITIONAL DISCUSSIONObservers in upper elevation terrain continue to report that wind slabs are becoming less reactive. This doesn't mean you should stop monitoring the effects of wind as you travel. As discussed above, you’re more likely to trigger a persistent slab avalanche where a stiff, wind-loaded slab sits over buried weak layers. Last Thursday, we found this type of snow structure during our site investigation of the fatal avalanche that occurred Wednesday in Baker Creek (see video at right, more details in the Forecast Discussion below). 

Avalanche Discussion

Today will be the warmest and sunniest day since the start of the January 10th storm cycle, and possibly of the new year. The effect of warming on persistent slab problems is not well understood. The theory is that warming temperatures—and especially direct sunshine—increase the strain rate at the snow surface which can concentrate stress on weak layers buried in the snowpack. Sound like a bunch of snow nerd gobbledegook to you? Me too, and I went to school for this stuff. Think of it this way: we've all seen that snow can do weird things when it warms up. It creeps down your card windshield, it slides off your roof, and it contorts and droops into odd shapes. This same behavior can impact buried weak layers when it happens on a slope. 

So while the effects of warming on persistent weak layers is complicated and poorly understood, it's generally accepted that it's not a good thing for persistent slab problems. To be on the safe side, I'd add slopes that are getting warmed by the sun to your avoidance list today.

Details from Wednesday's Avalanche Accident in Baker Creek:On Wednesday, January 15th, 2020, a snowmobiler was caught and killed in an avalanche in the Baker Creek drainage, approximately a half-mile northeast of Baker Lake. We visited the site Thursday to collect data on the avalanche. This video contains preliminary information collected during the site investigation; a full accident report will be published soon.

The avalanche released at an elevation of 9200 feet on a south-facing, wind-loaded slope. The slab broke 2-3 feet deep, 250-300 feet wide, and ran just over 600 vertical feet. The slope angle of the start zone was around 33 degrees, but the slope steepened significantly below the fracture line. The avalanche was triggered from lower on the slope, well below the crown line of the avalanche, and released on a persistent weak layer of faceted snow in the middle to lower snowpack. The avalanche debris range from 3-8 feet deep.

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