Bulletin d’avalanche

Stevens 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 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Continued snowfall and rising temperatures will maintain dangerous avalanche conditions at Stevens Pass. When combined with a potentially weak snowpack structure, slides could fail easily or break more widely than you're used to. Keep your terrain selection simple by avoiding slopes over 35 degrees where triggering an avalanche in new or old snow is more likely.

Problèmes avalancheux

  • Storm Slabs

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

    The snow is expected to keep falling at Stevens Pass, increasing the potential size of slabs. On Sunday, most reported avalanches were small, but they could start creeping into the large category by Monday morning. Whether it's your classic storm slab due to a warming trend making the snow upside down, a poor bond with the underlying surface, or maybe a wind slab, it doesn't really matter. You will want to steer around slopes over 35 degrees and convexities where triggering a slide is more likely. You can use small test slopes or quick handpits as you travel to look for potential points of failure and help understand how the snow reacts to your weight as a traveler. With various surfaces buried by this storm, you may find that the new snow has bonded differently from slope to slope. In some locations, avalanches could fail on weak snow, breaking more easily or widely than you're used to. You may even observe natural avalanches occur during or shortly after periods of heavy precipitation or wind. Slabs should be larger and possibly more reactive as you ascend in elevation or in wind-loaded terrain.

    (2/16/2025)

    Isolated test slopes produced shallow storm slabs that failed on a melt-freeze crust formed during last week's storm. Expect these to get larger on Monday.

    Photo: Katie Warren

  • Loose Wet

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

    Monday is supposed to be a touch warmer than Sunday, and the east flow may get scoured out. So that means there's a higher likelihood of a switch over to rain at lower elevations and in the western half of the zone. If you notice rain falling on dry snow, you may see rollerballs, pinwheels, or new fan-shaped avalanche debris soon afterward. Then you'll know it's time to head for lower-angled slopes, keeping aware of the terrain above you. 

    (12/28/2024)

    Wet snow instabilities, like these rollerballs and mini wet loose avalanches are a great indicator that it's time to head for lower-angled slopes. 

    Photo: Katie Warren

Avalanche Discussion

As of Sunday evening, the storm has been a bit lackluster compared to what was advertised at Steven's Pass. That doesn't mean it's been a total bust. A nice shot of snow covered the mountains, resulting in a handful of reported avalanches and good riding conditions. Steven's Pass Pro Patrol reported mostly loose avalanches during their morning mitigation work but observed small slabs in the neighboring backcountry later in the day. NWAC forecasters in the Henry Creek Clearcuts found that the bond at the 2/13 interface was variable but generally poor in areas where new snow had fallen over a subtle melt-freeze crust (mainly W and S aspects). There is still plenty of evidence of this week's wind event throughout the landscape.

There was no reported activity on our buried weak layers of concern. Some had hoped this storm would be a good test for the January Drought Layer (JDL) and 1/10. Uncertainty surrounds when (or if) the scales will tip, and avalanches will start occurring on these layers. NWAC forecasters found them roughly 2 feet below the surface on Friday, and snowpack tests were unremarkable despite the JDL being noticeably weaker than the slab above it. When these layers were first buried, there were numerous reports of whumpfing collapses and shooting cracks but no reports of associated avalanches in this zone. In zones to the south and west, multiple persistent slab avalanches were reported on the layer. Despite the lack of avalanches within our zone, you should consider them when making trip plans, at least until the storm ends. The added load from the storm may stress these layers, but it could be another avalanche or you finding the sweet spot that tips them over the edge. The snowpack likely won't warn you before this avalanche strikes, making it hard to pinpoint where or when it could happen. Stick with the travel advice from the storm slab problem by avoiding slopes over 35 degrees, and you should also be able to manage this hazard throughout the storm cycle.

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