Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Both dry and wet avalanches are in the cards for Monday. Move off and away from steep, sunny terrain if you see signs of wet avalanche instability like rollerballs and pinwheels. Downwind slopes will still hold day-old and maybe even new slabs of wind drifted snow.

Avalanche problems

  • Loose Wet

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

    The combination of new snow, sun, and rising temperatures is one of the most popular recipes for wet loose avalanches. The amount of wet avalanche activity will vary across the zone tomorrow. Areas farther south in the zone received more snow this weekend, will see warmer conditions Monday, and are therefore primed to see the most and the biggest avalanches. In other areas, you may just see some rollers and very small wet avalanches - but don't let down your guard.

    Pay attention to slopes overhead and look for initial signs of instability like snow shedding from trees and rocks. Though initially small, wet avalanches could grow in size or trigger a slab avalanche lower on the hill and run farther than expected. 

    Wet loose avalanches running long distances in alpine terrain.

    Photo: Jason Speer

  • Wind Slabs

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

    Very strong winds and 6-16” of new snow from this weekend’s storm built new wind slabs that still deserve respect Monday. Moderate winds and abundant new snow might create new ones on select slopes.

    Pay attention to the pattern of wind loading by using scoured snow surfaces, cornice-like features, and changes in snow texture to figure out where wind slabs lurk. Stiff, smooth snow surrounded by rougher surfaces is probably wind slab. You can use test slopes and other tools to evaluate the bond of wind slabs to the layers below - or just navigate around steep wind loaded terrain.

    Areas farther south in the zone and the volcanoes picked up significantly more snow and unstable slabs might still be found on all aspects, not just wind loaded terrain. Consider all steep terrain with 10” or more of new snow as suspect until proven otherwise. New snow slabs may also become more reactive during the initial phase of warming and sun exposure.

    (1/20/2023)

    Snowmobile triggered wind slab avalanche from Friday on Mt. Baker. The slab was two days old. Large triggers can still pull out a slab even after it becomes unreactive to the weight of a single person.

    Photo: NWAC Public Obs

Avalanche Discussion

New snow amounts varied across West South with 6-8” of dense new snow near treeline along the Cascade Crest compared to 12” or more of new snow around Paradise and Mt. St. Helens. Winds cranked overnight with gusts into the 50’s at White Pass and 40's at Crystal. Wind transport and shallow new slabs were observed at Crystal on Sunday. Wind slabs to 10" were reported from White Pass but they tended to be stubborn to unreactive to triggering during avalanche mitigation work.  

Prior to the most recent storm, crust developed on sun-exposed slopes while weak snow surfaces of facets and surface hoar were found on shadier slopes. It’s likely weak surface snow warmed and was destroyed by the wind prior to new snowfall. In areas where weak snow survives and is buried intact, you could find new slabs that are easier to trigger or release in surprising ways. Identify and investigate the interface between new and older layers and ease into steeper terrain by starting with smaller, less consequential slopes. 

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