Boletín de aludes

West Slopes South

Northwest Avalanche Center
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Peligro de aludes

Sat
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The volcanoes will get pummeled during this storm, resulting in High avalanche hazard. Throughout the zone, a variable and weak snowpack will make Friday more dangerous than your typical storm day. Adjust your mindset and your travel plans accordingly by stepping way back and avoiding avalanche terrain altogether if you see natural activity or are on the volcanoes.

Problemas de aludes

  • Storm Slabs

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

    High precipitation rates, strong wind, warming temperatures, and known weak snow on the ground are a recipe for very dangerous avalanche conditions. This will not be your run-of-the-mill storm cycle. The snow will likely be upside down due to rising temps, causing storm slabs. But buried weak snow will add a wicked twist to avalanche potential and your ability to manage the hazard. The variability in the distribution of weak snow will render our typical tips and tricks, such as using test slopes or handpits, ineffective. Use them to get a feel for the new snow, but don’t feel confident extrapolating those results to other locations. You could test a slope, walk a few feet, and find something completely different. We expect slabs will be larger and more prone to natural activity on the volcanoes where more than twice as much water is forecast than closer to the crest. When in doubt, avoid avalanche terrain altogether.

    (12/14/2024)

    A widely breaking storm slab over a crust that failed earlier this season on Mount Adams. This snowmobiler was caught and his sled was partially buried on a fairly small slope.

    Similar avalanches are expected this weekend. Some may be much larger.

    Photo: Jeremy Jouppe

Avalanche Discussion

As is often the case, the volcanoes will drive the hazard within the West South zone on Friday. With over 2 inches of water expected within a 24-hour block, it's hard to ignore the potential for large natural avalanches. With water numbers like that, we'd be forecasting High for most storms, but throw in rising freezing levels, wind, and known weak snow on and near the surface, and you've got a unique set-up that will likely result in unusual avalanches this time around.

Closer to the crest, all the elements are the same, except about half the water is expected (closer to 1 inch). It will be dangerous, and natural avalanches could occur during or shortly after periods of heavy precipitation or wind.  You may not find much hazard first thing in the morning, but as the snow stacks up, avalanche potential will rise quickly throughout the day, regardless of location. 

Over the past month, weak snow on and near the surface has been well documented within our zone. Before the storm, it was interspersed with variable surfaces like melt-freeze crusts or wind-affected snow. Weak grains, such as surface hoar and near-surface facets, haven't been an issue to date because they have lacked the slab to create avalanches. Well, that time has finally come. Slabs will develop on Friday and will be thicker in wind-loaded terrain or on the volcanoes. 

Unfortunately, the spotty distribution of these grains makes it difficult to use our standard indicators of aspect and elevation to point out where slabs could propagate widely this coming weekend. That said, snow will fall on a melt-freeze crust on slopes that typically see direct sunshine. This will make a great bed surface, and we are expecting a poor bond with the new snow. On shaded slopes, faceting (weak snow) has been more prevalent, so you may find slabs are touchier or break in surprising ways, spanning far distances or connecting terrain features. If you see the signs of persistent style avalanches, such as whumpfs or shooting cracks, get out of there!

After a month off, it's time we all get our heads back in the avalanche game and not ignore the basic fact that this storm setup is different than we're used to. We aren't jumping right into a persistent slab avalanche problem due to the spotty distribution of weak snow, but we may get there. If you’re a winter lover, we know you have pent-up desires after a lackluster January in the snow department. Be patient and dial your terrain choices way back.

If you've never submitted an observation before, this is the time. Please let us know what you see. We want pictures and information from every nook and cranny of our zone, whether you see an avalanche or not. 

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