Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

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

Spring meets winter with wetter snow down low and on sunny slopes, yet over a foot of dry snow at higher elevations, where you could trigger avalanches on wind-drifted features. Meanwhile, sun breaks will moisten the dry snow surface and wet loose avalanches will run naturally and with human triggers on steep slopes facing the sun. If you notice the sun getting snow moist and rollerballs running, steer around steep nearby slopes, where wet avalanches could run as deep as the mainly moist old snow surface. 

Avalanche problems

  • Loose Wet

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

    Dry, low-density snow will quickly become moist if we get sun breaks. On steep slopes, it will probably take only a few minutes from when the sun shines to when you start noticing rollerballs, which will then likely progress to wet loose avalanches.

    Stay aware of sky cover and snow moisture levels as you travel. Up high, where the snow is over a foot thick, rollerballs will at first stay small, but if enough snow is entrained and wet loose avalanches run, an avalanche could be as deep as all the way down to the old snow interface. Below treeline, where a shallower layer of new snow sits over the moist underlying layer, expect to see shallower swaths of the new snow layer running on the older layer beneath. Keep in mind that places you traveled earlier in the day may not be safe as the day progresses. 

    Wet loose avalanches like you might see on Wednesday. Notice they tend to start in areas that heat up faster, like around steep, rocky areas, or with tree bombs. 

    Photo: Lee Lazzara

  • Wind Slabs

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

    Near and above treeline you could trigger an avalanche in a recently formed wind slab. These deposits could be over a foot deep, although some new drifts could be shallower, with closer to 6" of snow avalanching with a human trigger. More than a foot of snow fell, and likely drifted into thicker deposits near ridgelines, around features, and in gullies.  We suspect the new snow layer bonded relatively well to the heavier, possibly moist, underlying layer, but newer drifts in the lower-density snow could avalanche with a human trigger. 

    Investigate the bond of the new snow over the old snow layer, and within new drifts of snow. Identify heavier or thicker-feeling snow, which may appear pillowlike or textured. Notice if your weight on the snow causes long, shooting cracks. If you find any of these thicker slabs, especially if there are accompanying indicators of weakness, steer around slopes steeper than 35° during your travels. There's a chance that a wet loose slide could step down, triggering a slab avalanche as well. 

    (12/18/2022)

    A small intentional skier triggered wind slab avalanche which occurred early afternoon near the start of our recent series of storms.  Baker backcountry.  6-12" crown. SS - ASc - R1-D1

    Photo: Adam Ü

Avalanche Discussion

Fourteen inches of snow was reported at Heather Meadows from overnight Monday through Tuesday afternoon. The underlying layer was noted as being moist, but much of the new snow was cool and relatively low density. Above around 6000ft, the old snow layer will probably be heavier but it may not be moist. Freezing levels are forecasted to drop to 1000ft Tuesday night, but due to a thick layer of new snow over the moist old snow layer, we suspect the old layer will remain insulated or "warm", and a crust isn't expected to form. 

Previous to the final push of cooler air which supplied us with the foot or so of new snow and almost an inch of water, we received 7" of water since Thursday. Most of this fell as rain, with the snowline mainly hovering in the 4000-5500ft range. There is likely several feet of snow up high. Large, natural wet slab avalanches occurred over several days, although most of the activity was likely on Sunday. Wet loose avalanches occurred many of these days as well. There is a small chance that glide avalanches could still run in suspect locations, which generally means steep, smooth rock slabs or grassy slopes. If you see glide cracks avoid traveling beneath them. 

Regions covered