Boletín de aludes

Snoqualmie Pass

Northwest Avalanche Center
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Peligro de aludes

Thu
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Lots of avalanches in the last 24 hours should key you into the fact that the snowpack is grumpy. Give it the time it needs to heal by keeping things simple on Wednesday and avoiding slopes over 35 degrees. Temperatures befitting of the shortest and darkest day of the year could pose a hazard on their own. Bundle up out there.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    The snowpack will still need time to adjust to the recent load from Tuesday’s storm. Slabs will be less than 24 hours old when you step out of your car on Wednesday and have been extremely reactive. You should use small test slopes, uptrack tests, or hand pits to determine how easily the snow is failing and if there is a poor bond to the underlying layers. Even if it is soft, snow that fails in blocks or produces a crown is in fact a slab and should grab your attention. 

    In more exposed areas, you may have to deal with thicker and stiffer Wind Slabs. Depending on your elevation, these may exist on different aspects, so look for freshly built cornices or smooth pillow-like piles of snow to help you identify wind-loaded slopes to avoid. Although these slabs are categorized differently, the way you should manage them is mostly the same. You should avoid slopes over 35 degrees where triggering a slab avalanche is more likely.

Avalanche Discussion

It was quite the active day at Snoqualmie Pass on Tuesday. We received several observations from NWAC forecasters, avalanche professionals, and recreationalists about how reactive the snow was in the morning hours. Unfortunately, almost every observation came from the same spot, the Kendall Trees area. Small slabs were failing naturally and easily triggered by skiers, sometimes remotely with long shooting cracks. Traveling through the terrain, you could find a small crown on almost every convex feature or unsupported slope. Similar reports came from skiers on the other side of Commonwealth Basin as well as up the Alpental Valley. We do not have any avalanche observations from upper elevations due to the ferocity of the storm.

While these slabs were generally small, most were triggered early on in the storm. As snow continued throughout the day on Tuesday, the depth of the layer where these failed has now increased to well over a foot below the surface. In wind-loaded areas, the depth could be much deeper. WSDOT’s avalanche team triggered some of these deeper wind-loaded slabs during their mitigation work on Tuesday afternoon and we heard of at least two avalanches large enough to bury or kill you in the backcountry.

Slabs appeared to be failing at the new/old interface with heavy snow over weaker snow, but the 12/18 interface also showed up in snowpit tests. Maybe this storm instability will settle out by day’s end, but it could only shift the problem to the lower 12/18 layer. With numerous reports of remotely triggered slabs and long shooting cracks in somewhat benign terrain, it would appear there is enough unsettled business in the snowpack that you should be paying attention closely on Wednesday. You may not have the in-your-face feedback of a crown on every convexity to fall back on now that they’re buried and filled in. Be sure to evaluate terrain carefully.

A general cooling trend and an end to the stormy weather await on Wednesday, and it should be downright frigid out there. If you’re in the mountains, be sure to dress appropriately and keep your partners in sight with all of this new snow. While no avalanches have been confirmed on our buried weak layers in the snowpack, we are still keeping them on our radar for the duration of the week and a large Glide type avalanche on Monday has us scratching our heads a bit.

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