Bulletin d’avalanche

West Slopes Central

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

Dangerous conditions exist, with human-triggered avalanches likely in the new storm snow on Monday. Around a foot of new snow exists, and you can expect to trigger avalanches on most steep slopes, especially in areas that are wind-loaded, where avalanches will be larger. Stay off all steep terrain, and avoid travel beneath large, steep slopes if you see natural avalanches, experience whumphing, or are remotely triggering avalanches. 

Problèmes avalancheux

  • Storm Slabs

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

    It's likely that you can trigger an avalanche the full depth of the new snow, around a foot or deeper, on most steep slopes. This isn't a day to try to thread the needle, just avoid traveling on slopes greater than 30°. If you remotely trigger avalanches, if you see natural avalanches, or experience whumphing then avoid traveling beneath large steep slopes as well. 

    Backcountry travelers in the neighboring West North zone reported triggering many small avalanches and a few large avalanches on all aspects on Sunday. Most were failing close to or just beneath the new snow layer. On steep south aspects, the avalanches ran just above a crust on a thin layer of small, weak, faceted snow.  As for other aspects, conditions were still touchy and avalanches were failing just under the new snow layer on a more subtle weak layer. Some slides were remotely triggered. 

    The West North received a little more snow than us, but we probably have similar weaknesses in this zone. Even the day after the bulk of the storm, expect conditions to remain spicy in the backcountry as this isn't just your normal storm slab avalanche problem- the weak underlying layers may stick around for a while and conditions won't stabilize as quickly as you may be used to. 

    (2/16/2025) A storm slab avalanche that war reported in the Snoqualmie backcountry on Sunday. This area was probably even more reactive, given the obvious visual wind-effect. 

  • Loose Wet

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

    Wet loose avalanches may run at lower elevations on Monday. We received THIS observation from near Sedro-Woolley, outside of the forecast zone, sharing findings of rollerballs. Avoid steep slopes and terrain beneath them if you see any nearby activity or in areas with moist or wet snow. 

    We may have missed the window because we suspect these types of avalanches were probably more active on Sunday than they will be on Monday, but keep wet avalanche activity in mind where the snow is moist or wet.

    (2/16/2025)

    Rollerballs are good indicators that wet loose avalanches may follow. 

    Photo: Nola

Avalanche Discussion

We're uncertain if an additional load of snow will awaken the Persistent Slab avalanche problem. The last known avalanche to occur on the weak snow that's buried about 2-4ft below the surface was on February 2. If we were getting several inches of water, especially rain, we'd be much more alarmed about avalanches stepping down or failing on the deeper persistent layers, but we don't believe we're quite there with seeing an uptick of avalanches on this layer, although it's not out of the question. Be mindful that mid and upper elevation slopes on the northerly half of the compass are where any deeper avalanches, probably unsurvivable, would likely occur.

Water numbers varied quite a bit in the zone, with about 6 inches to a foot of snow in most of the zone.  We'll continue to receive scattered showers equating to an inch or two Sunday night and Monday.  

If you get out in the backcountry, please share with us what you saw by submitting an observation HERE or on the Avy App. 

Régions couvertes