Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Even though this storm will only bring a few inches of powder to the West South zone, the wind should easily blow the snow into small fresh slabs. Watch for smooth pillow-like drifts on the lee sides of ridges and near exposed features to highlight potentially hazardous pockets you want to avoid.

Avalanche problems

  • Wind Slabs

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

    We aren’t expecting widespread wind slabs. These fresh pockets of wind-drifted snow will likely only occur in spots near ridges, on exposed features, and in rock-walled gullies. Blowing snow and sharp cornices can help you anticipate which aspects could hold small wind slabs. In these areas, locate smooth pillow-like drifts and go around them by using lower angled or less wind-affected snow. 

    In some locations, the new snow may not bond well to the old surface. As a result, some of these slabs could trigger very easily. Don’t let one of these small avalanches surprise you, especially in high-consequence terrain.

    (12/17/2022)

    Blowing snow in the Tattoosh Range near Mt Rainier, Saturday 12/17

    Photo: Andy Harrington

Avalanche Discussion

This isn’t a very big storm for the West South zone. We expect most of the moisture to stay to the north of the region. Even still, some locations could receive 2-4 in of fresh snow by Sunday afternoon. Outside of the wind-affected areas, you may encounter a few very small sluffs (loose dry avalanches) but these shouldn’t pose any real hazard. The new snow will fall on a wide variety of surfaces. Therefore, it could react a bit differently from one slope to the next. In exposed areas, strong winds prior to the storm sculpted the snow and formed a patchwork of textured surfaces, scoured slopes, and pockets of soft snow. On more sunny aspects, a breakable sun crust formed. In sheltered areas, this crust was often capped by surface hoar and facets. You may find that the new snow struggles to “stick” to this old surface and slides easily on the crust. In shaded areas at mid and lower elevations, large surface hoar was observed prior to this storm. The few inches of new snow may only help preserve this potentially new buried weak layer. While it shouldn’t be an issue on Sunday, it’s worth keeping an eye on as storm totals start to stack up this week. 

For the past several days, we’ve been forecasting a persistent slab problem in the West South zone. A lack of avalanches and no new significant snowpack test results gives us confidence that this layer continues to heal. While not totally impossible, an avalanche failing on the 12/8 surface hoar (12-20 in below the surface) would likely be a very isolated event.

Regions covered