Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Continued snowfall and wind should be enough to maintain dangerous avalanche conditions in the West South zone. The highest hazard areas remain in the south where more recent snowfall has occurred and the next storm system will hit first. Regardless of your location, you’re most likely to trigger a slab avalanche in wind-loaded terrain so keep an eye out for shooting cracks or wind-stiffened snow as signs to head for lower-angled slopes.

Avalanche problems

  • Wind Slabs

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

    You may need to manage Wind Slabs of varying ages on Sunday. To complicate matters, they’ll likely be on an assortment of aspects due to the wind reversing direction multiple times recently. New slabs could build throughout the day as winds drift recently fallen snow onto leeward slopes or other notorious wind-loaded features such as convexities or confined gullies. Look for actively blowing snow, smooth pillow-like mounds, or textured surfaces to help identify the wind-loaded slopes you should avoid. Additionally, you could encounter lingering slabs from Thursday night’s wind event hidden a few inches below the surface. You’ll need to feel for subtle changes in the stiffness of the snow to identify these ones. They may feel hollow and be more difficult to trigger, but if they fail they’ll likely be larger and could break in more surprising ways. 

    (3/11/2023)

    A naturally occurring slab avalanche at the base of a cliff band near Crystal Mountain. Avalanche professionals suspect this slide may have stepped down to a deeper layer.

    Photo: Joe Hoch

Avalanche Discussion

The storm waves keep on crashing into the West South zone. This weekend is a relative lull compared to the end of the last work week and what’s in the near future. That said, we’re still squeezing out a few inches of snow per day accompanied by some gusty winds. On Saturday, backcountry travelers around the zone found roughly 2 inches of new snow being drifted into fresh slabs. NWAC forecasters and avalanche professionals in the Crystal Mountain backcountry reported triggering shallow Wind Slabs on steep slopes and older stiffer slabs from Thursday’s major wind event. Shooting cracks were produced with uptrack tests and reverse loading/double cornice lines were observed due to the wind direction switch.

Sunday should be a similar kind of day, with a few inches of new snow and generally light to moderate wind speeds. Accumulations should once again be highest on the volcanoes. You may notice temperatures starting to slowly creep up ahead of a larger incoming storm system. Be leery of overhead cornices that have grown large during the recent windy weather. They could fail and trigger avalanches on the slopes below. With a cold and clear night forecast for Saturday evening, weak surfaces may develop and could possibly get buried by Sunday’s light snow showers. If so, these grains could produce some surprising shallow avalanches.

The past week has delivered several rounds of precipitation yielding anywhere from 2-3.5 feet of snowfall around the West South zone. Combined with numerous wind events coming from every direction, the upper snowpack now contains multiple storm interfaces, thin sun crusts, and is a bit upside-down in places. On Saturday, NWAC forecasters identified weak surface hoar buried below newly formed Wind Slabs. We have been messaging that the upper snowpack has been generally stable for much of the week due to the lack of a significant slab. That narrative has changed in recent days. And with the biggest storm wave about to impact the zone on Sunday night into Monday, we anticipate that it will likely tip the scales for many slopes.

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