Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Though the rain storm may begin to ease, dangerous and unpredictable avalanche conditions will continue on Monday. Destructive and deadly natural avalanches remain a possibility at all elevations. Steer clear of steep open slopes, and if you have to cross beneath an avalanche path, do so quickly and one at a time. If you head out, expect soggy, difficult travel.

Problèmes avalancheux

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    The full menu of wet avalanche problems—wet slabs, wet loose, and glide—remains on the table Monday. Even if the spigot from the sky slows, liquid water will continue working its way through the snowpack, testing its strength and stability as it percolates and pools. 

    Wet avalanches, especially wet and glide slabs, are notoriously hard to predict. While the frequency of avalanches may have already peaked by Monday morning, the size may not have. Even if you don't observe signs of previous large avalanche activity, a destructive slide could release on its own and without warning. Avalanches are mostly likely to originate in the upper and middle-elevations, though they could easily descend down into the lower elevations. With so much recent snow stacked over the late February AR crust, some slides could run thousands of feet, breaking trees as they charge into valley bottoms. Even wet loose avalanches that start out small could gouge deeply into the snowpack and grow plenty large enough to bury a human as they descend.

    Due to the combination of consequence and unpredictability, the avalanche conditions on Monday won't be "manageable". Consider avoiding any path or runout, and if you must cross a path, do so by moving quickly and with a purpose. Given the truly horrendous travel conditions on offer on Monday, the best option is to give the mountains some time. 

    (3/2/2025)

    A wet slab avalanche from the late February Atmospheric River in the East North Zone. These slides can run incredible distances, well into valley bottoms. 

    Photo: Katie Warren

Avalanche Discussion

Though we have limited observations from the backcountry, the theme throughout the zone is rain and warm temperatures. It was raining at the top of Alpental by midday on Sunday and a wet slide of some variety was reported just out of bounds. The rain/snow line will continue to rise above all forecast elevations overnight as the unfrozen liquid keeps hammering the mountains around the Pass. Rain-on-snow=avalanches, and this equation should be on your mind no matter what you see in the mountains on Monday. 

Water takes time to percolate through the snowpack and there are many interfaces above the late February AR Crust where it could pool, destabilize the snow, and trigger an avalanche. In many parts of the zone, that process is only just beginning as of Sunday afternoon. We suspect a more widespread cycle may occur this evening and overnight. The timing of avalanches will play out differently depending on the previous snowpack structure and the quantity and rate of liquid water introduced into the snowpack. Once the water is in there, it is really challenging to know what it will do and how the snowpack will respond. What we do know is that it takes time, and this process will not have run its full course by Monday. Don't let an absence of prior avalanche activity lull you into thinking that a large avalanche couldn't release. Wet avalanche concerns will be with us in some form or fashion until colder temperatures return.

All in all, the message right now is simple: Monday isn't the day to try and outsmart this problem. 

Régions couvertes