Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Large, surprising wet snow avalanches remain a concern as the tail end of this warm, wet weather pattern travels through the area. If you see glide cracks or large, sagging cornices give the terrain beneath these features a wide berth. Snow may fall at upper elevations later in the day, and wind could redistribute the fresh snow into reactive drifts which you might be able to trigger an avalanche on. 

Lawinenprobleme

  • Glide Cracks

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–2.5

    Glide avalanches characteristically fail at the ground, often in areas where smooth rock slabs or low shrubs are lubricated by liquid water. You may see a glide crack, usually near the top or middle of a steep slope, as an indicator that the slope below could release as an avalanche soon. Back in my early ski patrol days I saw a large glide crack at the ski area one morning. I went to check it out on my next lap, and by the time I got there I found a large avalanche debris pile and a slick, grassy bed surface. I'm glad that the avalanche hadn't occurred while I was investigating it. Now I stay far away from glide cracks and areas beneath them.  On the other hand, some glide cracks can sit around for days or weeks but change minimally. It's tough to tell whether a glide crack will release quickly or not at all, and this is a good reason to exercise extra caution around them. 

    As rain continues to fall and temperatures remain relatively warm, beneath one of these glide cracks, or a large, overhanging, cornice, is no place to be. Steer around steep slopes where you find these features. Avoid or travel quickly across the flats beneath glide cracks and cornices. 

    An example of glide avalanches releasing from steep, rocky slopes, similar to what might happen on Tuesday.

    Photo: Mark Allen

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–1.5

    A lot of water is coming in the next 24 hours. Hopefully we're not being too optimistic by saying that temperatures will be dropping and it could end as snow, especially at higher elevations. Winds will be strong enough to redistribute new snow into reactive slabs.  We're not quite sure how well snow will stick to the old, previously moist surface. In some areas it may stay in place, while in other locations, especially where wind redistributed the snow into thicker, heavier slabs, the snow could slide near the old snow surface. 

    You can probably identify where wind deposited fresh new slabs. Drifts could be speckled across an unusual rain-sculpted landscape, filling in gullies, or sitting in pillows on leeward sides of features and ridgelines. Depending on how much snow and wind we get, avalanches could stay inconsequential in size, or they could grow so large that if you trigger one it could carry and bury you.

    It's up to you to determine how deep the slabs are, and identify whether the snow bonds well to the underlying layers. You can quickly isolate a column above the old snow layer with your hand and see if any new layers easily pop off or if they stay stuck to the underlying snow.  Long, shooting cracks indicate the snow layer could avalanche on a steep slope. If your steps cause long, shooting cracks or you find layers that aren't bonded well to the underlying snow in large enough patches, avoid slopes greater than 35 degrees. If the slab is only a few inches thick it's probably not enough to cause a problem, but when it starts getting a bit deeper that's when enough snow could be present to take you for a scary ride .

    Shooting cracks like these coming from skis, snowshoes, feet, etc are indicators that a reactive wind slab exists.

    Photo: Matt Primomo

Avalanche Discussion

Snow depths are shallower at lower elevations, as I found during a trip to Highway 20 near Newhalem with a WSDOT team on Monday when we investigated slide paths that ran down to the road. Some below treeline spots might not hold enough snow to avalanche. In other areas, avalanches could be smaller. However, if you’re on a lower elevation adventure in or near mountains, be aware of crossing gullies that could connect with a large avalanche path far above you. This was notable during the Hwy 20 visit, as the road which had been closed before the warming event had a few large avalanches running from above treeline elevations down tight gullies to the low elevation road. 

Warm wet weather arrived early Christmas Eve after a week of cold temperatures and feet of dry, low-density snow fell. When temperatures first warmed and rain began falling a large avalanche cycle probably occurred. I saw evidence of a few early warming event avalanches when I investigated Hwy 20. The weather has been so wild since Friday that almost no one has made it into the mountains, and we aren't quite sure what's going on out there. Precipitation isn't letting up until Wednesday, when temperatures will finally drop to more seasonal norms. A glide avalanche cycle could be continuing until we have had a good freeze on the snowpack, although we aren't really sure. Glide avalanches are scary and unpredictable. Until we have more information or temperatures cool, continue to make conservative decisions in the backcountry.

Travel will be challenging, with soft, punchy snow. You can expect to find flooding and an overall wet day. Surfaces may freeze and become slick at upper elevations. If you get out, even on a low elevation hike, let us know how much snow there was and if you saw any recent avalanches. You can submit an observation HERE. 

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