Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

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

Kernpunkte

It's still possible to trigger a slab avalanche in wind-drifted snow.  Use lower-angled terrain to navigate around steep features where you identify signs of wind drifting or see pillowy-looking wind slabs. Cold temperatures persist with strong east winds in some parts of the zone. Be prepared to deal with an injury or gear failure where you can't rely on movement to keep you warm.

Lawinenprobleme

  • Wind Slabs

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

    Strong westerly winds on Thursday shifted to the north and east overnight. The result was fresh wind loading and multiple natural and human-triggered avalanches on southeast through west aspects. While slabs should be harder to trigger on Friday, they are still out there, especially on slopes approaching 40 degrees or on unsupported slopes.

    Locations farther east in the zone - or near major mountain valleys - will see strengthening winds and fresh slab formation by the afternoon as east winds grow stronger. Fresh slabs will be easy to trigger. You might even see a few natural avalanches as well.

    Use the standard clues like cornices and wind-scoured surfaces to identify the loading pattern around you.  Active loading will be observed in locations with higher wind speeds. Hand shears and test slopes on small, wind-drifted features can give you a sense of slab reactivity. Move cautiously if you head into more aggressive terrain. Even though there might be no wind-drifted snow where you enter a steeper slope, that doesn’t mean you won’t find it a short distance away.

    Touchy wind slabs were dense, chalky and looked a little like this.

    Photo: Simon Trautman

Avalanche Discussion

 

Backcountry travelers triggered a  handful of small and one larger slab avalanche in different zones around Hwy 542 on Friday. Also, very large natural avalanches - that probably released with wind loading overnight - were observed on the west and south aspects of Goat Mountain and also high on the southwest side of Shuksan.  On the other hand, plenty of steep lines were ridden on north and east aspects with few results. Another interesting aspect of the day's avalanche activity was how the sun seemed to increase the slab reactivity. One observer stated, "I imagine the refresh from the wind was a factor but the sun seemed to be the magic ingredient today."  

While quite calm in the Baker BC, observers north of Hwy 542 found much different conditions with stiff, wind-affected snow everywhere and stubborn drifts to 5' deep. If you haven't noticed it was also super cold on Friday. Pan Dome saw a low temperature of -16F Friday morning and the Brown Top Snotel recorded a low of  -26F. Brrrrr . . . . . Despite the cold temperatures, full sun on Saturday will slightly warm sheltered solar aspects. Keep an eye out for signs of instability related to warming.

While recent wind slabs are the type of avalanche you are most likely to encounter,  there is a low chance you could trigger a very large slab avalanche no matter if a slope is wind-loaded or not. A layer of facets overlying the 12/30 melt-freeze crust is now buried 3-5’ deep in many locations. Avalanche activity associated with this interface is decreasing, but recent control work pulled out a slab avalanche 3-5’ deep. There is also the possibility that larger natural avalanches observed Friday are related to the 12/30 as well.

Use caution approaching big slopes in the coming days and get a handle on snowpack structure and recent avalanche activity before considering more complex terrain. As usual with lingering persistent weakness, the likelihood of triggering is low. If you were to trigger one it would be with a very large load or in very steep, unsupported terrain.

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