Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

A warm wet storm could create dangerous avalanche conditions in some parts of the zone Thursday. You may encounter natural wet avalanches near and below the rain snow-line. These slides could be larger and more common near the volcanoes where more precipitation is expected.

Avalanche problems

  • Loose Wet

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

    Expect to see loose wet avalanches near and below the rain-snow line. This means some of the most dangerous conditions could occur at mid and lower elevations. If you encounter wet mushy snow, see new rollerballs, or find fresh piles of fan-shaped debris then steer away from nearby steep terrain and limit any time you spend underneath it. 

    Natural loose wet slides are most likely in places that receive significant rain and during periods of heavier precipitation. With all the recent cold snow on the ground, some of these slides could grow larger and pose a real danger to any traveler in their path.

    (1/14/2023)

    Example: You could see natural wet slides like this at lower elevations. NW aspect ~4300'

    Photo: NPS Rainier Rangers

  • Wind Slabs

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

    You may find a few small wind slabs along ridges and in exposed terrain by Thursday afternoon. Fortunately blowing snow and fresh cornices should make potentially wind-loaded slopes pretty easy to anticipate. Look for pillow-like slabs and snow that looks thicker in these areas to identify the pockets you want to avoid. While these slabs should stay relatively small and shallow, they will continue to grow during the day and may trigger easily on the underlying cold dry snow.

    (3/31/2023) Signs of wind-loading near a chute. Photo: Andy Harrington

Avalanche Discussion

Thursday’s warm wet weather will be an abrupt change from this week’s cold and showery pattern. In general, we’re expecting this storm to favor Mt St Helens and Mt Rainier. You should see the greatest danger, biggest avalanches, and most natural activity in and around these mountains. However, this is still a big change for the snowpack, and even those areas receiving less precipitation should experience some natural avalanche activity. The storm should peak Thursday afternoon/evening with the heaviest rain/snow and warmest temperatures. This will likely cause the avalanche danger to peak in the afternoon hours. 

One unique feature of this setup is the cold, dry, and layered snowpack. While you may find a crust on the surface on sunny aspects and at lower elevations, below the top few inches conditions look much more winter-like. This makes us a little uneasy about how the snow will handle this big change. We could start to see wet slab avalanches in a few areas. If you see slabs failing near and below the rain-snow line, the problem has morphed into a much more dangerous beast. Dial it back, and seek out terrain away from steep open slopes.

Over the past few days avalanche activity around the West South zone has largely consisted of several small natural loose wet slides and a few intentionally triggered wind slab avalanches. In general, 1-2 ft of settling snow sits over the 3/31 interface. At least initially, this is the primary snow available for wet avalanches.

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