Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Saturday should be a relative break in the stormy weather as winter storms wrap up before an atmospheric river heads our way. Wet and dry avalanche problems could exist on slopes over 35 degrees. Larger slabs and a greater likelihood of triggering them exist on the volcanoes.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Slab avalanches may be easier to trigger in the morning as an overnight storm wraps up.  After a generally warm Friday, temperatures should start to drop, which could result in lower-density snow on the surface. While this snow could fail in slabs or loose, you'll also need to look for deeper layers from the past several days as potential weak points in the upper snowpack. The rising and falling temperatures mean a new crust could exist below Friday night's storm snow, creating an excellent bed surface for avalanches to run on. Springtime weather has delivered periods of graupel, which can act as a short-lived weak layer. Use uptrack tests, small test slopes, and quick hand pits to gauge the upper snowpack's slab potential. If blocks fail easily in your tests, you find a poor bond at the new/old interface, or discover an upside-down snowpack (heavy snow over weaker snow), then you should avoid slopes over 35 degrees where triggering a slab is more likely.

    Slabs will be larger and possibly more reactive on the volcanoes or wind-affected terrain.

    (3/21/2025)

    A slab avalanche in Pickhandle Basin near Crystal Mountain. This one looks to be in wind-loaded terrain.

    Photo: Dallas Glass

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    There's a decent chance of extended periods of sunshine on Saturday. Fresh snow could destabilize if that happens, resulting in wet loose avalanches. If the snow surface gets sticky and wet in the sun, you may see rollerballs, pinwheels, or snow shedding from trees and rocks. These precursors to wet avalanches should be your sign to head for lower-angled terrain, staying aware of what's above you. Wet loose avalanches often start at a point but fan out and grow in size as they descend. Much like the storm slab problem, a crust at the base of the new snow could provide an excellent sliding surface for these avalanches to travel far distances and grow large. In isolated locations, they could gouge down into older snow layers.

    In areas where the snow surface is already wet and moist, you may be able to push wet snow to create an avalanche on steep slopes.

    (3/12/2025)

    We avalanche activity the day after a storm earlier this month. Similar activity could occur on Saturday.

    Photo: NPS Rangers

Avalanche Discussion

Saturday will be a complex weather day, with competing factors vying to influence the snowpack. In the morning, we'll be wrapping up a storm, which should deliver fresh snowfall accompanied by wind on a cooling trend. Then, the sun is expected to come out for a few hours late morning through midday. Lastly, we'll be clouding back up as an atmospheric river approaches, which should decimate our snowpack on Sunday. Saturday night may not be the time to take that winter camping trip. Avalanche hazard will quickly rise and become very dangerous once the next storm arrives.

The upper snowpack around the zone varies in depth over our last atmospheric river (AR) crust. We have had measurable precipitation at our core weather stations almost daily for roughly a week and a half, resulting in several feet of recent storm snow. Before Friday, the storm snow was generally right-side-up and setting. Storm interfaces were highlighted in snowpack tests but did not show much propagation. However, Friday's warm storm threw a heavier load on top, creating an upside-down scenario that resulted in both natural and human-triggered avalanches. This could lead to an uptick in slab activity on Saturday on steep slopes. You should also keep an eye out for sensitive cornices at upper elevations. On the volcanoes, avalanche potential is a notch higher. Our friends at the USGS relayed that numerous large to very large avalanches have occurred this week on Mount St. Helens, some traveling long distances from the upper mountain to lower-elevation terrain.

Apart from the constant parade of storms in March, we've also seen an uptick in avalanche involvements around the state and within our zone. Numerous backcountry travelers were caught and carried within the last week - some were partially buried. Parties often described conditions as "sneaky" or "surprising" when recalling their experiences. Since the upper snowpack and weather are so variable, you should constantly reassess conditions throughout the day. Even if slopes appear similar, they may act in very different ways.

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