Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Strong east winds formed fresh slabs at mid and upper elevations. Identify and avoid steep slopes holding recently wind drifted snow. You are more likely to trigger an avalanche on terrain features like convex rolls and unsupported terrain above and around cliffs. Danger from wet loose avalanches should still factor into your plan for the day.

Avalanche problems

  • Wind Slabs

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

    Widespread wind transport and loading was reported Tuesday. Wind speeds and slab formation will decrease but the fresh wind slabs will need a few days to strengthen. Wind slabs may be easier to trigger where they formed over a crust or weak facets and surface hoar .

    Cornices and other clues that show the usual direction of wind loading - normally from the south and west - might not be useful to determine where fresh wind slab lurks. Instead look for recently scoured ridgelines with smooth, fat, or pillowy-looking drifts on the slope below. Test slopes and hand shears will help gauge wind slab reactivity and depth and can help you identify areas where they are easier to trigger. 

    (3/8/2023)

    Smooth wind slab on the left and scoured snow on the right.

  • Loose Wet

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

    After Tuesday’s wind event, there is way less loose snow laying around to react to warming, especially at upper elevations. Still, it’s spring and when the sun is out snow can warm up and then fall down. You are more likely to see wet avalanches on slopes facing the sun. Lots of slopes have produced wet loose avalanches but that doesn't mean there can't be more with additional warming.

    They are more likely to naturally release when the snow is wet and unsupportable. You might even get one moving on a steep slope.  Wet loose avalanches commonly initiate in rocky or treed terrain. Keep an eye on what is above you and limit time spent on or below steep slopes of wet, sloppy snow.

    (3/27/2023) Natural wet loose avalanches from the weekend and big, overhanging cornices.

Avalanche Discussion

Even though avalanche conditions are not necessarily dangerous or tricky, there is still plenty of uncertainty going into Wednesday.  Did wind slabs form over a weak snow surface near treeline? Is there enough soft snow left above treeline to react with warmer temperatures, clear skies, and calm winds? Or has the wet loose avalanche problem played itself out in the last four days? Maybe wind slabs will become more reactive with some warming?

Observers at Schriebers/Baker NRA saw significant wind transport building up slabs on west facing slopes. Open slopes were well scoured out by the wind and they stuck to more sheltered terrain after briefly working their way up to 6000'.  A team on the White Salmon Glacier found identical conditions and ended up turning around at the same elevation.  Snowmobilers at Excelsior in Canyon Creek found less windy conditions and north aspects holding onto to favorable snow conditions. No natural avalanches were reported from anywhere in West North, but it's difficult to imagine there weren't at least a few out there given the extent of wind transport.

The biggest snowpack factor is a layer of faceted grains that sits below the new snow from late last week but above a crust that formed on all aspects about a week ago. In most places they were dispersed by strong winds prior to the last storm, but not in all. Though no avalanches were directly linked to this layer, reports of whumphing, test results showing propagation, and a slightly unusual pattern of avalanche activity are will keep it on the list of things to look for this week.

 

 

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