Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Saturday should be the start of a warm and sunny weekend in the West South zone. As the snowpack starts to adjust to this weather change, your mindset should shift from dry to wet avalanche problems. If you are in the sunshine and the surface is getting wet and sticky, then you’ll know the time has come to consider wet avalanches on slopes over 35 degrees.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    It's been a windy week in the West South and that should continue on Friday night into Saturday morning. You could find some shallow Wind Slabs have formed on leeward slopes or near rocky features such as cliffs and gullies. Lingering slabs that formed over the past week should be on the mend, but continue to be leery of slopes below cornices or wherever you find wind-stiffened snow. Using visual clues such as textured snow surfaces or drifts behind objects can help key you into where fresh slabs may be lurking. If you suspect that a feature is wind-loaded, avoid it and similar terrain.

    (2/4/2022)

    This unstable pocket of wind drifted snow was intentionally triggered by NWAC forecasters in the Tatoosh Range on Friday. Notice how it is on a convexity.

    Photo: Dallas Glass

  • Loose Wet

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

    Temperatures are expected to rise throughout the day and many areas should see plenty of sunshine. In areas further south such as Mount St. Helens, this warm up could be more accelerated than areas further north. Regardless of your location, the warm up could cause the  snow surface to destabilize on sunny slopes, resulting in wet avalanches. A wet and sticky snow surface, followed by rollerballs and pinwheels will be your first indicators that the time has come to put these avalanches on your radar. Wet Loose avalanches often start at a point, such as from snow shedding from trees and rocks, and fan out as they move downhill. As they descend, they are capable of entraining significant snow or triggering slabs. With plenty of snow available for entrainment above the Late January Crust and some uncertainty around persistent grain types at this interface, be sure you are managing terrain well by avoiding features over 35 degrees if you notice these avalanches.

    (2/4/2022)

    Sunny slopes started to shed surface snow and produce small Wet Loose avalanches on Friday near Crystal Mountain.

    Photo: Shane Robinson

Avalanche Discussion

NWAC forecasters in the Tatoosh Range found variable conditions including, powder, wind-affected snow, and ice on Friday. They observed blowing snow and shallow fresh Wind Slabs building at upper elevations and were able to confirm the weak snowpack structure we have been talking about near the Late January Crust. On Thursday, professionals near Crystal Mountain reported a thin surface crust had developed on all aspects up to ridgeline and that the snow was gaining cohesion over the Late January Crust. On Friday, slopes that see direct sunshine near Crystal already began to shed and produce Wet Loose avalanches. As we continue to transition toward warm and sunny weather, these observations tell us that lingering dry problems still exist, but we will increasingly be dealing with wet issues. The time of this transition will depend on your location, but all areas of the zone should be dealing with warm temperatures and full sunshine by Sunday.  As this transition happens, keep in mind that freshly built cornices or blocks of snow and ice will be more likely to fail during times of warm and sunny weather.

We expect all avalanche activity, whether it be wet or dry, to occur above the Late January Crust. We have identified a weak snowpack structure at this interface but have no confirmed avalanches on this layer as of Friday evening. The easily identifiable layer can be found roughly a foot below the surface and the weak “facet-crust sandwich” should be more prominent on slopes that do not see direct sunshine. If avalanches were to initiate on these persistent grains, they could fail in surprising ways by breaking above you or spanning further distances than you may be used to. You should take the time to dig in the snow with your hand or shovel to take a look at this layer and how it is reacting before stepping into consequential terrain. 

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