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

On Sunday, you're more likely to trigger an avalanche in wind-loaded terrain or on unsupported slopes. The threat of weak layers buried several feet deep and releasing without warning should be shaping your travel plans. Resist the urge to travel on open powder-filled slopes where one of these catastrophic avalanches could occur. 

Avalanche problems

  • Wind Slabs

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

    Wind slabs could exist on a variety of aspects on Sunday due to shifting winds. In some cases, you could find a wind-loaded pocket on both sides of the same ridge. Pay attention to changes in the density and depth of the snow as you travel. Firmer or thicker areas are likely wind-loaded and should be avoided. Visual clues such as fresh drifts, cornices, and textured surfaces can give you clues to local wind patterns. Winds slabs like to form near ridgelines, along the base of cliffs, and at the tops of chutes. Since the shifting winds and fresh snow may make these slabs challenging to identify, your best bet may be to stick to sheltered terrain where wind-loading is less likely.

    At lower elevations and in sheltered areas, you're more likely to find lots of deep powder. Expect dry loose slides that could knock you over or push you into a tree. 

    (3/2/2024)

    A deep (up to 4 foot crown) wind slab avalanche triggered by explosives at Crystal Mountain. It's on a fairly convex and unsupported slope. 

    Photo: Crystal Mountain Pro Patrol

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3

    This is the problem that should be shaping your travel plans on Sunday. There's been plenty of bulls-eye information from the past few days that weak layers now buried deep in the snowpack have been coming to life. Natural and human-triggered slides have occurred on the Early February Crust and other layers just above it near Crystal Mountain. Snowpack tests at White Pass and Paradise have resulted in sudden and clean breaks on these layers. In neighboring zones, avalanches on these layers have been triggered remotely and even resulted in a fatality on Friday.

    The distribution and likelihood of triggering are a bit difficult to pin down, but most avalanches have occurred above 5500ft. These weak layers were widespread throughout the landscape when they formed but have morphed over the last month due to sun, wind, and other meteorological factors. Slides this past week have failed on a variety of aspects (NW-SE). They have been erratic and unpredictable, making it almost impossible to identify which slopes are primed and ready to release. Your best management tool will be to avoid large open slopes and their runouts where one of these wide, deep, and deadly avalanches could occur.

    (3/1/2024)

    A deep avalanche near Bear Gap in the Crystal Mountain backcountry. [N 6200']

    Photo: Andy Harrington

Avalanche Discussion

Preliminary Report: An avalanche accident occurred on Friday, March 1, near Darland Mt in the Ahtanum Meadows area. Two snowmobilers were involved in the slide. One rider was fully buried and killed. The avalanche occurred around 6600ft in a generally east-facing bowl. NWAC staff will visit the accident site on Saturday. Our deepest condolences to the family, friends, and community.

We're on a slow downtrend in weather inputs, with less wind and snow forecast. But Sunday will be eerily similar to Saturday - cold temperatures, more low-density snow, shifting winds, and the occasional sun break. Expect more wind and snow the further south in the zone you are, such as Mount St. Helens. Old storm interfaces should continue to settle and heal while new ones develop above them. It will take some time before our deeper layers of concern can be put back to bed. During longer sun breaks, the surface could warm, resulting in avalanche activity on sun-exposed slopes.

This past week, multiple feet of snow fell and came close to doubling our seasonal snowpack. Now several feet below the surface, a weak structure continues to lurk. Facets and surface hoar on the 2/19, 2/14, and Early February Crust (EFC) could all produce avalanches. To date, most observed avalanche activity has been near Crystal Mountain. However, the USGS has passed along several observations of very large avalanches occurring on all of the volcanoes in our zone. On Friday, NWAC forecasters at White Pass received sudden results when testing our persistent weak layers. National Park Rangers at Paradise reported sudden and planar test results when investigating the EFC on Saturday. 

Add it all up, and we're dealing with a lot of new snow, which has resulted in complex avalanche danger and deep snow immersion (SIS) potential. You'll have to exercise extreme patience and diligence not to be lured onto open slopes by powder fever. Don't trust your life to a single hole in the ground. And tracks on a slope are not a good indication of stability. Persistent slabs are tricky and can fail without warning. Keep your partners in sight at all times, and be sure they don't tip into a treewell or get stuck in a spot they can't climb out of. 

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