Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Buried weak layers could result in unpredictable, high-consequence avalanches. This problem won't give you much warning and isn't one you can outsmart. The only option is to avoid large open slopes where they're more likely. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2

    Buried weak layers exist throughout the zone and should be your primary consideration when making travel plans on Sunday. These layers are 2-3 feet below the surface and have produced whumpfing collapses as recently as Friday. Their distribution may be a bit spotty, but shaded slopes at mid and upper elevations are generally suspect. Avoid large open slopes in these areas, electing to travel in small, low-angled, or treed terrain instead. You may not get much feedback from these layers, warning you that a slope is ready to slide. Conditions may "feel safe" as you travel in the beautiful new snow, with no whumpfs, shooting cracks, or collapses. Don't be lulled into a false sense of security. The weak snowpack is lurking, and the only way to manage this problem is through avoidance.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    As snow continues to trickle in daily, new snow problems should be on your radar on slopes over 35 degrees. Wind-loaded slopes should be the most likely location to trigger an avalanche large enough to call consequential. Look for stiffer-feeling snow near ridgelines, the base of cliffs, or the sides of gullies/chutes. Use visual clues to help identify wind-loaded features to avoid, such as actively blowing snow, textured surfaces, fresh cornices, or drifts behind objects. You may find thicker and more sensitive slabs on the volcanoes than in other parts of the zone.

    In sheltered terrain, you may see loose avalanches running in the surface snow. Some of them may be solar-induced during sun-breaks. Most of these should be small enough to call inconsequential but don't get caught off guard near a terrain trap.

    (2/7/2025)

    A shallow wind slab just below ridgeline in the Crystal Mountain area.

    The textured surface and relative stiffness compared to the surrounding low-density snow are easy ways to identify wind-loaded features.

    Photo: Josh Lipkowitz

Avalanche Discussion

Over the past week, we have had a steady trickle of bulls-eye information alerting us that the snowpack is unhappy. Whumpfing collapses and persistent avalanches have been reported from many of the usual observation points in our zone, including Mount Adams, Mount Rainier, White Pass, and Crystal Mountain. The January Drought Layer (JDL) and 1/10 complex are the buried weak layers causing all the commotion. As alluded to in the persistent slab problem above, their distribution is a little spotty, and they may look different from slope to slope. But generally speaking, they're 2-3 feet below the surface and consist of multiple melt-freeze crusts and facets (weak snow). We have watched these layers since they got buried last weekend, and there hasn't been much change. You know, they've persisted. So, in response, not much has changed in the avalanche forecast or how you should manage them.  Keep your terrain selection simple and try to fight the lure of new snow on slopes you know are potentially dangerous. Test results continue to suggest that these layers can propagate a fracture given the right trigger, including propagation saw tests repeatedly failing with cut lengths around 35 cm [PST35 END].

Roughly 2-6 inches of light and fluffy snow fell around the zone on Saturday, increasing the depth over our weak layers and giving the snow surface a nice little refresh. Above the persistent issues, the snowpack is generally right-side-up with a few interstorm layers and subtle melt-freeze crusts. NWAC forecasters reported shallow wind slabs near ridgelines and actively blowing snow on Friday. A few small avalanches were reported on Saturday, including a decently sized dry loose. Expect more of the same on Sunday. You should manage the upper snowpack like typical post-storm snow on slopes over 35 degrees. Just remember what's below it.

Regioni coperte