Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Dynamic weather conditions, complex and overlapping avalanche problems, and a weak snowpack will combine to create dangerous avalanche conditions Monday. Choose simple easy-to-manage terrain where you can quickly identify and avoid places where avalanches travel if needed.

Avalanche problems

  • Storm Slabs

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

    Warming temperatures, additional snow, and moderate winds will create an upside-down snowpack. You need to manage this problem in the morning while it's still snowing. Look for strong over weak snow by using hand pits, small slopes, and uptrack tests. Given the recent small storms, you may need to investigate deeper than just what falls overnight. You could trigger an avalanche on any steep open slope at mid and upper elevations. In areas with more than 10” of recent snow and in wind-affected terrain some of these slides could be large enough to bury and kill you. 

    While we don’t expect a widespread natural storm slab cycle, you could see a few avalanches, especially near the volcanoes. This will be most likely during periods of heavy precipitation,  warming temperatures, and as snow changes to rain.

    (3/20/2022)

    Cracking in the recent storm snow suggest you have strong over weak layering. 

    Photo: Rainier NPS Rangers

  • Loose Wet

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

    As the rain-snow line rises through the terrain, wet avalanches will take the lead as your primary hazard. By the end of the afternoon, this will likely happen for all but the highest slopes in our forecast area. For a day like Monday, you’re may to see both loose wet and wet slab avalanches. Fortunately, your response is the same. When you find wet sticky snow or see new avalanches, dial it back and stay off of and out from under steep slopes. We expect most of the natural avalanche activity to stay small, but you could see a larger avalanche in big complex terrain and where more snow accumulated over the past few days.

    (3/1/2022) Example: A wet slab avalanche from our last rain on snow event. . Photo: Dallas Glass

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–2.5

    It’s hard to say exactly how the persistent weak layer will react to the load from this storm. For most locations, we’ve been slowly adding snow all week. While Monday’s system is big for the Volcanoes, the crest will continue this incremental loading. Given the highly uncertain nature of this avalanche problem, best to give it a wide berth. Avalanches this past week have been remotely triggered from adjacent terrain and ridgelines. So, put plenty of room between you and any steep open slope on W-N-E aspects near and above treeline.

    (3/17/2022)

    A large avalanche that failed on 3/16 near Crystal Mountain. This slide failed on the 3/8 facets and ran on the Early March Crust, with debris crossing a popular traverse track.

    Photo: Robin Pendery

Avalanche Discussion

Given the dynamic nature of Monday’s storm, this isn’t a day to mess around. Choose terrain that lets you easily identify avalanche terrain, and quickly reduce your exposure as conditions change. This includes making sure you have a safe route back to the trailhead if things become more dangerous than expected. Some uncertainty exists around how much precipitation most areas of the West South zone will receive. If more water falls than expected, natural avalanches could become much larger and more common creating locally very dangerous conditions. 

We expect the volcanoes to take the brunt of this storm. Even though that may mean less snow near the Crest, given the presence of a persistent slab issue, you’ll likely still encounter potentially dangerous conditions. Over the past several days human triggered avalanches and audible whumpfs have been observed across the West South zone. A layer of sugary facets just above the Early March Crust has been the culprit in all of these events. In most locations this layer is now 2-3 ft below the surface. While this may make it harder to trigger and avalanche could easily be big enough to bury and kill you. Unfortunately, there aren’t a lot of ways to easily rule this avalanche issue out. Tracks on a slope and a few snowpack tests do not mean its safe. Best to just give this hard to manage problem the respect it deserves. 

At lower elevations, less snow will limit the size of avalanches. Instead you may find sticky snow, firm rough surface, open creeks, and piles of avalanche debris.

Regions covered