Avalanche forecast

West Slopes South

Northwest Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 2 years ago.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

Highlights

Difficult to predict avalanches on buried weak layers continues to be the primary issue within the West South zone. Make travel plans that steer you well away from large open slopes where this problem is more likely. A lack of observed avalanches or whumpfing collapses does not indicate stability; the poor structure is well documented.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    This is the problem that should drive your terrain selection. A well-documented weak snowpack exists throughout the zone below all the light and fluffy storm snow. The big question mark revolves around the likelihood of triggering. Can humans trigger this layer a few feet below the surface, or will it take something larger like a cornice collapse or a new storm? The answer isn’t clear, but don’t take the gamble. We have had multiple human-triggered and natural slides this week failing on persistent weak layers. Your best bet is terrain avoidance.  Stick to small low-angle or treed slopes where this problem is less likely. Triggering one of these slides in large open terrain would have devastating consequences. 

     

    (2/3/2025)

    A skier triggered persistent slab avalanche near White Pass. This slide released over a 100ft wide and 2-3ft deep. WNW, 5600ft SS-ASu-D2-R2-O

  • Wind Slabs

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

    Above our weak interfaces, there is plenty of recent storm snow. You’ll likely need to manage it on slopes over 35 degrees, and it could look different depending on your terrain. We’re calling it a wind slab since wind-loaded slopes will be the most likely location to trigger an avalanche large enough to call consequential. Look for actively blowing snow, fresh cornices, or large pillow-like drifts to help identify wind-loaded features to avoid. You’ll likely notice that the snow is stiffer in wind-affected terrain than the light and fluffy snow elsewhere. 

    Speaking of the low-density storm snow, in sheltered terrain you may see loose avalanches running in the surface snow. Some could fail during periods of sunshine or due to snow shedding from trees and rocks.

    (2/6/2025)

    Snowmobilers observed wind-textured snow on Mount St. Helens on 2/6. The obvious ripples indicate that wind slabs could exist in leeward terrain.

    Photo: Chris Benelli

Avalanche Discussion

Thursday was a bit of a break in the storm action for the West South zone. White Pass and Crystal Mountain Pro Patrols reported actively blowing snow and shallow wind slabs near the crest. Cornices are starting to build out again, and a few even failed naturally. Snowmobilers reported good riding conditions in the flats but observed plenty of wind effect on the slopes of Mount St. Helens. With plenty of snow available for transport, expect this trend to continue over the next few days, even with light wind speeds. Backcountry travelers reported relatively low-density snow away from ridgelines and minimal signs of instability in well-treed and low-angled terrain. The sun came out and triggered some loose avalanches on steep sun-exposed slopes. 

It was our first day since the stormy weather started a week ago without a report of a whumpf, collapse, or persistent avalanche in our zone. Does that mean that this problem has been put to bed? Absolutely not. Although the January Drought Layer (JDL) and 1/10 complex didn't give direct feedback for a day, they are still down there and considered weak. Test results continue to suggest that these layers can propagate a fracture given the right trigger. These layers are roughly 2-3 feet deep, and the poor structure trumps any snowpack tests or lack of whumpfing you experience. 

The storm snow above the JDL is mostly right-side-up but contains some weak points that could fail in the right terrain. Our relatively benign weather could help some of these typical storm layers start to heal, but it won’t be enough to cure those persistent problems. It remains to be seen if sunshine helps the storm snow “slab up,” inching us closer to more avalanche activity.

Regions covered