Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Recent avalanches on deeply buried weak layers combined with new snow and wind make for dangerous avalanche conditions. Steep, open slopes facing east, north, and west can produce avalanches large enough to bury, injure, or kill. Stick to lower-angle terrain or head for the forest, where you'll find fantastic snow and safer conditions. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Since Saturday, we have received nearly daily reports of natural and human-triggered avalanches across multiple locations in the West South. Some have propagated widely, breaking up to three feet deep on well-documented weak layers buried in January—avalanches like these are often unsurvivable. While most notable results have been on the northern half of the dial, we don't yet have full confidence that you couldn't find this problem on an isolated south-facing slope, especially on slopes that are somewhat locally protected from direct sun. The nature of this problem alone should be enough to shape your travel plans, even in clear weather. With more snow and wind Wednesday and overnight into Thursday, a conservative tour plan is essential.

    While the formation of these problems is complex, the strategy for staying safe is simple: don’t try to outsmart this one. Even if you don’t see recent avalanches or experience cracking or collapsing, don’t let your guard down—the snowpack is still dangerous. Tracks don’t mean a slope is safe, snowpack tests may not reveal the problem, and you may not see obvious warning signs before a slope releases. Keep it simple—avoid steep, open slopes facing west, north, or east.

     

    (2/1/2025)

    This intentionally triggered persistent slab, propagated the entire width of the feature on a ENE slope at 6200ft. It failed on facets over a thin crust. Getting caught in an avalanche like this could prove unsurvivable.

    Photo: Dallas Glass

  • Storm Slabs

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

    Another round of snow with increasing winds means that storm and wind slabs should be on your radar. Even if new snowfall doesn't amount to much, there are large quantities of snow available for wind transport which could add to the hazard. Slabs will be most sensitive in steep wind-loaded terrain below ridge lines, cornices, cliffs, and at the tops of gullies and chutes. Given the knee-deep depth of soft and unconsolidated snow out there, soft storm slabs could be a problem at all elevations, even out of the wind zone. By avoiding the persistent slab problem, you will also avoid the brunt of any storm/wind slab instabilities. If you are traveling in steeper terrain on the southern half of the compass or in the forest, feel for hard over soft snow and look for signs of wind-loading like blowing snow, textured surfaces, and lens-like deposits, and avoid slopes where you see those signs. Dry loose avalanches could also run fast and far in the fresh snow. An appearance by the sun may cause some show to shed from trees or make dry loose avalanches a bit more likely.

    This problem isn't the main hazard on Thursday, but, triggering one of these slides could step down into deeply buried weak layers and trigger a more substantial and consequential avalanche. 

    (2/1/2025)

    An intentionally triggered small storm slab. 3-12" deep, and 20 feet wide. SS-ASc-D1-R2-S, NE, 6200ft

    Photo: Dallas Glass

Avalanche Discussion

On Thursday, NWAC forecasters in the Crystal backcountry reported a rumbling whumpf (would-be avalanche if the slope was steeper) on a west-facing slope at 6100ft. A long time backcountry traveller in the touring party called it "the loudest whumpf I've ever heard". They also reported unstable results from numerous propagation saw tests on ESE, W, and N aspects above 6000ft (yes, also ESE). Combine that with a report from Crystal Pro Patrol of a likely skier-triggered persistent slab avalanche from either Tuesday or Wednesday and the picture is clear. We know the problem exists at Rainier and White Pass, and now we have clear evidence of the problem at Crystal as well. These avalanches can fail up to 3ft deep, and perhaps even more after a fresh round of wind-loading. We have no reason to believe the issue doesn't exist at Mount Adams and St. Helens as well. 

Sometimes these problems present with a rumbling roar, and other times they make themselves known with a more discomforting growl. In the West South, we are somewhere in between. None of that matters though. Don't wait for your own rumbling roar to convince you to dial things back. With a problem like this, it's a numbers game. Many slopes won't avalanche, some will, and there is no safe way to manage a problem like that. You have to avoid it. Remember, structure trumps individual pit results, and this snowpack structure isn't good. A 2-3.5 ft slab of snow has buried the weak January Drought Layer (JDL) comprised of facets, crusts, and surface hoar, depending on location. A bit below is the also suspect 1/10 crust complex complete with facets on top and within. Either of these layers could fail, it doesn't really matter which one. More snow and wind could make avalanches more likely on Thursday, but even you don't find lots of new overnight snow, keep it mellow.

With a conservative tour plan that avoids steep open terrain on the northern half of the compass, you don't need to dig a pit to stay safe and have a great day in the mountains. If you do decide to dig, the purpose should be to help build a dataset that shows trends over time, not to clear a slope as stable. When we all put our observations together, overtime, we may be able to further isolate this problem to specific aspects or elevations. But, at the individual level, a pit is highly variable, and test results should not be used to assess a specific slope as safe. Remember, we didn't get here overnight, and this problem won't magically go away overnight either. 

Please help us hone in on this problem by submitting an observations. All obs are helpful, whether they involve a pit or not!

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