Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Wednesday’s dynamic weather conditions should keep you alert as you manage lingering pockets of wind drifted snow and an incoming storm. Watch for smooth firm pillow-like drifts you may want to avoid. Because recent winds blew from nearly every direction, you could encounter these wind slabs on any aspect and in some unusual locations.

Avalanche problems

  • Wind Slabs

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

    Backcountry travelers this week continue to report wind slabs on a variety of aspects and features. This isn’t much of a surprise since the wind seems to continually bounce between east, west, and south. So, while these lingering pockets of wind drifted snow may be harder to trigger, their potentially unusual locations could keep you on your toes. With the recent storm snow, some of these slabs could be 1-2 ft thick and big enough to bury you. So, watch and feel for older wind-affected snow. Sharp drifts and textured surfaces can help you anticipate wind-loaded areas. Then steer around firm pillow-like drifts and seek out lower angled or less wind affected slopes to avoid these potential avalanches. 

    As precipitation starts to fall in the afternoon, strong and gusty winds will no doubt blow the new snow around. You could see new shallow wind slabs forming later in the day. While these drifts may be much easier to trigger than the lingering older slabs from above, their small size will limit their hazard. Don’t let the blowing snow distract you from watching for signs of the deeper and more dangerous older wind-loaded pockets.

    (4/18/2022)

    This wind-loaded pocket cracked on a test slope well below ridgeline on a west aspect. 

    Photo: Dallas Glass

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Even though you may see sunshine in the morning, it will need to overcome chilly temperatures and a stiff breeze to break down the frozen surface. We don’t think this will result in more than a few rollerballs. However, at lower elevations rain in the afternoon, may easily cause natural loose wet avalanches. This precipitation-induced wet hazard is the one you want to pay attention to. It will be most likely in locations that receive more rain (like the volcanoes) and later in the day. Rollerballs and small piles of fan-shaped debris serve as the easiest clues that this problem is developing. While these slides should remain small, don’t let them push you into a creek or over a cliff.

    (3/11/2022) Example: rain on snow triggered these rollerballs earlier this winter. Photo: Dallas Glass

Avalanche Discussion

Wednesday will be a bit of a transition day between storms. Your biggest hazard should come from the snow that fell Monday night and Tuesday morning. Generally 6-10” of snow accumulated around the West South zone over the 4/18 interface. On many slopes, the bottom of the storm may be marked by a melt-freeze crust. This can be a good snowpack marker to use to investigate the recent snow with hand pits or small slope tests. Below the 4/18 interface, you should find 2-3 ft of settled, generally right-side-up snow sitting on the 4/8 crust. While we think avalanches Wednesday will only involve the most recent storm snow, we are continuing to track this upper snowpack as we head into a period of warmer weather. 

Sun breaks on Tuesday caused rollerballs and small loose wet avalanches on some southerly slopes. This is a great indication that the surface on these aspects became wet and sticky. Clear skies and cool temperatures Tuesday night should allow this to freeze and should form new surface crust by Wednesday morning. 

While sun breaks first thing in the morning may start to soften the snow, increasing clouds and a chilly breeze should quickly put an end to any impacts of the sun. Rain and snow should spread across the zone by mid to late morning and create wind conditions especially for locations near the Cascade Crest. Expect poor visibility and wind weather to make travel challenging particularly at mid and upper elevations later in the day.

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