Boletín de aludes

West Slopes South

Northwest Avalanche Center
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Peligro de aludes

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

Lo esencial

This storm cycle will continue to focus on the West South zone on Monday, particularly the volcanoes. Deeper layers of concern could wake up with additional loading and shouldn't be ignored when making travel plans. You're more likely to trigger avalanches on slopes over 35 degrees or in wind-loaded terrain.

Problemas de aludes

  • Storm Slabs

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

    Continued snowfall will only increase the potential size of slabs throughout the zone. Slabs will be larger in wind-loaded terrain or on the volcanoes where storm totals are higher. Whether you encounter a classic storm slab due to a warming trend making the snow upside down, a poor bond with the underlying surface, or maybe a wind slab, it doesn't really matter. You will want to steer around slopes over 35 degrees and convexities where triggering a slide is more likely. You can use small test slopes or quick handpits as you travel to look for potential points of failure and help understand how the snow reacts to your weight as a traveler. With various surfaces buried by this storm, you may find that the new snow has bonded differently from slope to slope. In some locations, avalanches could fail on weak snow, breaking more easily or widely than you're used to. You may even observe natural avalanches occur during or shortly after periods of heavy precipitation or wind. 

    (2/15/2025)

    A handful of natural slab avalanches were reported on Mount Adams on Sunday. Many of them occurred near rocky features or on convex slopes.

    Photo: JB

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2

    Uncertainty is the central theme when discussing our persistent weak layers. They have been dormant for over a week, but snowpack tests and observations indicate they haven't healed much. This storm should provide a good test for the January Drought Layer (JDL) and 1/10 complex. Those are the facts. The uncertainty surrounds when (or if) the scales will tip and avalanches will start occurring on these layers. If you've written these layers off recently, you should again consider them when making trip plans, at least until the storm ends. The added load from the storm may stress them, but it could be another avalanche or you finding the sweet spot that tips them over the edge. The snowpack likely won't warn you before this avalanche strikes, making it hard to pinpoint where or when it could happen. Stick with the travel advice from the storm slab problem by avoiding slopes over 35 degrees, and you should also be able to manage this hazard throughout the storm cycle. 

Avalanche Discussion

This storm hit differently across our large zone. The volcanoes are hovering around a foot of new snow, while over at Crystal, a hard block by Rainier means considerably less snow has fallen. White Pass is hovering right in the middle. The new snow is not evenly distributed across the landscape due to periods of moderate winds. The snowpack structure was essentially the same heading into the storm, and last week's savage east wind event impacted most areas. The difference is the amount of snow from this storm over the 2/13 interface. It seems obvious, but you'll find larger avalanches and higher hazard in areas with more snow (roughly 8" or more). 

On Sunday, backcountry travelers on Mount Adams reported a handful of natural avalanches on convexities and near the base of rocky features. Up at Paradise, more natural activity was observed in the storm snow at mid-elevations and small wet avalanches at lower elevations. Over at White Pass, we got a report of cornices on atypical aspects, wind drifting, and moist snow. Other observations noted the ferocity of the storm and poor visibility. It is certainly warmer than it has been over the past few weeks. No activity was reported on our persistent weak layers on Sunday. However, NWAC forecasters have noted that the JDL and 1/10 complex remain essentially unchanged. Based on recent test results and observations, the focus is slowly shifting from the JDL to the 1/10 complex. Once the storm clears, we may get answers on whether these layers reached their tipping point.

On Monday, the warming trend should continue even as the West South experiences the brunt of the final wave of this storm cycle. Don't be surprised to see mixed precipitation or even a changeover to rain at lower elevations, possibly resulting in some wet avalanche activity similar to what was observed near Paradise on Sunday.

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