Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
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Out of date — this forecast expired 4 years ago.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

Another day of favorable weather should help the snowpack continue to heal. You’re most likely to trigger an avalanche on wind-loaded features such as convexities or confined gullies. On more open slopes, don’t get tripped up by a loose avalanche near terrain traps. 

Avalanche problems

  • Wind Slabs

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

    We’re anticipating the most likely location for you to trigger an avalanche on Wednesday will be on slopes where the wind has drifted snow into stiffer slabs. Look for Wind Slabs near ridgelines, on convex features, or near rocky terrain such as the base of cliffs or confined gullies. These slabs should be slightly stiffer than the surrounding low-density snow but likely won’t be Hard Slabs. Feel for changes in the consistency of the snow as you travel to help you identify the areas we’re concerned about. Wind-loaded features may look “pillow-like” or “fat” compared to the surrounding terrain and you might notice some textured surfaces nearby. If you suspect a slope to be wind-loaded, simply choose a simpler route to avoid it.

    (2/8/2023)

    Example: A Wind Slab avalanche that released a day after our previous storm.

    Photo: Shane Robinson 

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    A mostly sunny day on Wednesday means solar-induced loose avalanches could again present a problem. These avalanches start at a point and fan out as they move downhill. They’ll be most likely on steep slopes over 35 degrees that see direct sunshine and could be preceded by rollerballs or pinwheels. You may see them initiated by snow shedding from trees or rocks even if the snow surface isn’t wet and sticky - manifesting more like a Dry Loose. Regardless of the moisture content, their behavior and management remain the same. If you notice the signs, don’t get tripped up by one in consequential terrain and you can always head for shadier slopes to avoid them altogether.

    (2/11/2023)

    Example: small loose avalanches and a few rollerballs on a steep sunny slope. These ones originate near trees and rocks.

    Photo: Andy Harrington

Avalanche Discussion

This storm dropped variable snowfall amounts across the West South zone, with the volcanoes once again outpacing areas closer to the crest. Observations are basically non-existent from the zone for Tuesday, so we’re not without uncertainty. But looking at NWAC weather stations and the general weather trends, we feel confident that the storm snow should be healing and you will need to start focusing more on specific features rather than open slopes. 

On Monday, Crystal Mountain Pro Patrol relayed that the storm did not start with rain on Sunday evening, resulting in a firm crust at the base of the storm snow. In most other areas of the zone, this doesn’t appear to be the case. A warm and wet surface from liquid precipitation likely created a favorable bond once the switch was made to snow later early Monday morning. Be sure to take a look at this interface (2/13) and the new snow above it on Wednesday when you are making your slope scale evaluations of stability. This is the snow where we anticipate most avalanches to occur. You can find the 2/13 around 5-8” below the surface near the crest and around a foot deep on the volcanoes. On slopes that see direct sunshine, a slight crust may have formed on the surface. Shadier slopes will likely continue to harbor cold dry snow.

If you're out and about, please let us know what you're seeing out there so we can paint a better picture. 

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