Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Due to a variable and weak snowpack, Friday will be more dangerous than your average storm day. Don’t roll out your usual playbook and travel plans. Instead, dial them way back and consider avoiding avalanche terrain altogether. High hazard is expected to develop by the end of the day, particularly at upper elevations.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    1–2

    High precipitation rates, strong wind, warming temperatures, and known weak snow on the ground are a recipe for very dangerous avalanche conditions. This will not be your run-of-the-mill storm cycle. The snow will likely be upside down due to rising temps, causing storm slabs. But buried weak snow will add a wicked twist to avalanche potential and your ability to manage the hazard. The variability in the distribution of weak snow will render our typical tips and tricks, such as using test slopes or handpits, ineffective. Use them to get a feel for the new snow, but don’t feel confident extrapolating those results to other locations. You could test a slope, walk just a few feet, and find something completely different. This will be an all-snow event at upper elevations, and we expect slabs will be larger and more prone to natural activity due to additional wind loading. When in doubt, avoid avalanche terrain altogether.

    (1/11/2025)

    One of the numerous slab avalanches that occurred last time we got snow over a crust. Weak snow was suspected to have been involved in at least some of the slides that day.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    It wouldn’t be a Snoqualmie Pass storm this season without the possibility of rain at lower elevations. The questions are: how much snow is already on the ground if a change over to rain occurs, and how high up does the rain reach? The answers will dictate the size and location of any potential wet avalanches. Luckily, you’ll know if rain is falling on dry snow in your area, alerting you that these slides may soon follow, and you should head for lower-angled terrain.

    (1/5/2025)

    Wet avalanche debris from a rain-on-snow event earlier this month. This slide came close to a popular hiking/snowshoeing route to Lake Annette.

    Photo: Evan Wendel

Avalanche Discussion

The storm is here, and it’s forecast to be a doozy. If you’re a winter lover, we know you have pent-up desires after a lackluster January in the snow department. That was certainly unusual weather, creating an unusual snowpack. So now that we’re back in the storm track, we’re left with the potential for unusual avalanches. Heavy snowfall and strong winds will be accompanied by a bump in freezing levels mid-day, possibly resulting in mixed-precipitation or rain. You may not find much hazard first thing in the morning or at lower elevations. However, as you ascend and the snow stacks up throughout the day, very dangerous conditions, including natural avalanches, are expected to develop quickly.

Over the past month, weak snow on and near the surface has been well documented within our zone. Before the storm, it was interspersed with variable surfaces like melt-freeze crusts or wind-affected snow. Weak grains, such as surface hoar and near-surface facets, haven't been an issue to date because they have lacked the slab to create avalanches. Well, that time has finally come. 

Unfortunately, the spotty distribution of these grains makes it difficult to use our standard indicators of aspect and elevation to point out where slabs could propagate widely this coming weekend. That said, snow will fall on a melt-freeze crust on slopes that typically see direct sunshine. This will make a great bed surface, and we are expecting a poor bond with the new snow. On shaded slopes, faceting (weak snow) has been more prevalent, so you may find slabs are touchier or break in surprising ways, spanning far distances or connecting terrain features. If you see the signs of persistent style avalanches, such as whumpfs or shooting cracks, get out of there!

After a month off, it's time we all get our heads back in the avalanche game and not ignore the basic fact that this storm setup is different than we're used to. We aren't jumping right into a persistent slab avalanche problem due to the spotty distribution of weak snow, but we may get there. Dial your terrain choices way back, and please let us know what you see.  If you've never submitted an observation before, this is the time. We want pictures and information from every nook and cranny of our zone, whether you see an avalanche or not. 

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