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

Another round of wind and snow will create dangerous avalanche conditions in the West South zone on Saturday. You will be more likely to trigger an avalanche in wind-loaded terrain, on convex rollovers, or on steep slopes over 35 degrees. If the sun makes an appearance in your area of the zone, wet avalanches may develop.

Avalanche problems

  • Wind Slabs

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

    Stormy weather Friday night into Saturday should deliver fresh snow and moderate to strong winds to the West South zone. Expect Wind Slabs to develop on leeward slopes near ridgelines, on convex rollovers, or near rocky features such as cliffs and gullies at all elevations. You can use visual clues such as actively blowing snow, textured snow surfaces, or freshly built cornices to help you identify wind-loaded slopes to avoid. Although wind-loaded terrain could be the most likely location to trigger an avalanche on Saturday, that doesn’t mean that you can’t trigger an avalanche on slopes over 35 degrees or convex rollovers in wind-sheltered terrain. Use small test slopes and hand pits as you travel to test the reactivity of the recent storm snow and avoid slopes over 35 degrees if you find a poorly bonded interface or suspect wind-loading.

    (3/20/2021) Using visual clues is a great way to help identify the potential for Wind Slabs.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Although cool temperatures and mostly cloudy weather should dominate the day, if the sun makes an appearance, expect wet avalanche problems to develop. This may be more likely near the crest than on the volcanoes. Regardless of your location, avoid slopes that see direct sunshine if you notice the snow surface getting sticky and wet, see fresh rollerballs, or recent avalanches with fan-shaped debris.

    (3/12/2021) Rollerballs like this are a great sign that the snow surface has become wet and unstable. Photo: Robin Pendry

Avalanche Discussion

The storm on Wednesday night delivered up to 8” of snow to the West South, which was drifted into deeper piles by strong winds and sits atop a stout crust on most aspects (4/7 interface). With incoming snow thickening the slab depth over this interface, and possibly creating new potential weak layers, you will need to check all of the recent storm snow down to the 4/7 for instabilities on Saturday. We expect all avalanches to occur above this point, whether they are dry or wet in nature. Springtime weather is dynamic and could cause the snow to shed off rocks or cornices to collapse, so limit your time spent under these overhead hazards.

On Friday, multiple skier-triggered avalanches, including an involvement where a skier was caught and carried, occurred in the neighboring Snoqualmie Pass zone. This caps a week that saw multiple avalanche involvements and near-misses around the Cascades, including in the West South where a snowboarder was caught and carried by a large avalanche on Mount St. Helens. We continue to bring up that the snowpack has not made its full transition to a springtime snowpack, and this past week provides proof of that with both dry and wet avalanches driving these involvements. As we navigate our way through springtime weather, the transitions between dry and wet avalanche problems can be rapid and unpredictable, just like the weather. It can make decision-making and forecasting challenging since you can’t bring your winter mindset or spring mindset to the mountains to rely on for any given day. Perhaps the best advice is to learn from these recent incidents and dial back your terrain choices until more stable weather and snowpack patterns prevail.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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