Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 5 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

An uptick in wind could redistribute low-density snow into fresh new deposits, mainly at higher elevations. Search for actively blowing snow, wind-affected surfaces, and clues like long shooting cracks, and steer around new drifts on steep slopes, especially if you're in extreme terrain without a gentle runout. An overnight freeze will result in morning crusts on the southern half, which may soften as the day continues. 

Problèmes avalancheux

  • Wind Slabs

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

    An increase in wind and an abundance of low-density snow on shady aspects means newly formed small wind slabs could exist. You could trigger an avalanche on one of these new drifts. This is most likely to happen in featured, extreme terrain. If you trigger an avalanche in high-consequence terrain, even a small avalanche could take you for a rough ride. 

    There is 6-10 or more inches of low-density snow sitting on shady aspects available for transport, ready to load or crossload other areas. Slabs might build on a melt-freeze crust, which could provide a good sliding surface. Small new drifts of snow will likely deposit around features, on steep rolls, and in gullies. Drifts might be a few inches, or possibly a foot or more in depth. They may have a textured surface, or alternatively, a smooth, pillowed look to them. 

    Search for obvious clues like shooting cracks. Dig down with your hand to see if new slabs break easily on the underlying layer. Where you find any indicators of a slab that could slide easily, shift to lower-angle terrain. 

    Example photo: Small new wind slabs could form around features or in gullies. They probably won't be big enough to bury you, but they could take you for a scary ride in extreme terrain. 

    Photo: Adam Ü

Avalanche Discussion

Wednesday was a stormy day, with 6-10 or more inches of snow and reactive wind slabs. There were a few distant large and very large slab avalanches that failed naturally. Wind slabs became stubborn by Thursday, and on Friday, we were mainly seeing wet loose avalanches on steep slopes facing the sun. HERE is an observation providing many of these details from Heather Meadows on Friday. A fresh crop of wind slabs will likely keep our wind slab concerns elevated for Saturday. 

Beneath the new snow layer lies a series of crusts formed during warm periods in recent storms. These crusts have combined into one or are close to that through mid elevations in many spots. Slopes that received sun on Friday got wet, and will likely form a crust Friday night. It will stay a little cooler and be cloudier on Saturday, so we don't expect as much softening. If it's sunnier than expected, steep slopes facing the sun still might be able to produce a small wet loose avalanche with a human trigger, especially in areas near rocks. 

Another uptick in wind and a few inches of snow are expected by the end of the day Sunday, with cooler temperatures to remind us winter isn't quite over yet. If you make it out over the weekend, remember that our unseasonably thin snowpack still has many hazards even through mid-elevations, with open creeks and holes in abundance. 

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