Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Keep an eye on how the snowpack changes as sunshine and temperatures begin to increase. Recent storm snow over a crust is a good recipe for a variety of avalanche problems, so be leery of slopes over 35 degrees. Even in the shade, wind-loaded, unsupported, or convex features could produce avalanches that may break in surprising ways. 

Problemi valanghivi

  • Wind Slabs

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

    The most likely location to trigger an avalanche is in wind-loaded terrain. Slabs should be larger as you ascend in elevation or on the volcanoes. Look for textured surfaces, areas that look "fat" with pillow-like drifts, new cornices, or drifts behind objects to determine wind-loaded features to avoid. The base of cliffs,  sides of gullies/chutes, and convexities are all common features where the wind likes to deposit snow. Use small test slopes to gauge how the snow reacts to your weight as a traveler and quick hand-pits to investigate the bond to the 1/10 crust. Wherever you find wind-loading or a poor bond, you should divert to a lower-angled route.

    (1/12/2025) 

    Plenty of wind-effect and a skier-triggered slab in the White Pass backcountry on 1/12.

     Photo: Matt

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    The sun is going to come out and we're on a slow warming trend. It won't be blazing hot but may be warm enough to kick off avalanche activity on sun-exposed slopes. Look for rollerballs, pinwheels, new fan-shaped avalanche debris, or even the surface snow starting to "slab up" in the sunshine. Luckily, it will be easy to manage your exposure to any of these solar-induced issues by heading toward shadier aspects and keeping aware of what's above you.

    (1/12/2025)

    Avalanche activity on a steep sun-exposed slope on Sunday. Expect more of this in the coming days.

    Photo: CVT Crag Rats

Avalanche Discussion

After a snowy and windy start to the weekend, we're starting the work week off high and dry. Snow totals weren't overly impressive during our last storm, but they fell on a firm crust throughout much of the zone, creating the 1/10 interface. Reports continue to indicate that clean failures occur at this interface with hand shears and uptrack tests. The bond has been called moderate by some avalanche professionals and poor by others. Before committing to a slope, you need to take a moment and investigate this layer.

Most avalanche activity should be on the smaller side, but in isolated locations, slabs could break widely or act in surprising ways if they fail on weak grains above the 1/10 crust. Before the storm, surface hoar and near-surface facets were found above the 1/10 and could have survived the wind and onset of precipitation, resulting in a poor bond. In other locations, it may just be that the storm started warm, and rimed particles are taking their time to solidify their bond to the underlying crust. Regardless of the science behind it, be leery of unsupported, convex, or wind-loaded slopes until time and the warm weather have helped this pesky interface heal.

Before this storm, travel conditions were very challenging due to breakable crust, icy slopes, frozen tree bombs, and piles of avalanche debris. The new snow has helped, but many of these hazards are now only a few inches below the surface, making them more difficult to spot.

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