Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Avalanche danger may just barely rise into Moderate as new snow and wind build through the day. Snow at lower and mid elevations may start soft but will freeze over time. At higher elevations, wind-drifted snow could slide easily on firm layers below, and avalanches will likely be small, but consider steering around thicker drifts if you're above terrain traps. 

Problèmes avalancheux

  • Wind Slabs

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

    Wind slabs could grow to six inches or a foot by the end of the day. They will mainly exist at higher elevations, where underlying surfaces could be firm and smooth, resulting in small slabs that could slide easily with a human trigger- leaving you with only those firm surfaces beneath the small amounts of soft new snow. 

    Drifts tend to build on the leeward side of ridges, around rocky outcroppings or subtle features, and in gullies. They could surprise you by quickly shifting from very soft, non wind-affected surface just inches away. Search for smooth,  "pillowed" drifts, or alternatively, textured surfaces, as ways to identify where wind has drifted snow. Deposits will be shallow, a good time to use small test slopes and hand pits to see how easily the snow slides on the underlying layer. 

    If you're caught in a slide, it probably wouldn't be big enough to bury you. Your biggest hazard is traveling in high-consequence terrain, where a small slide could send you off a cliff or through rocks or trees, causing serious harm. If there's more than a few inches of fresh snow, consider steering around areas where drifts could build above terrain traps. 

    Wind deposits thicker drifts around rocky outcroppings. You're more likely to trigger an avalanche in areas like these. 

    Photo: Oliver Kramer

Avalanche Discussion

We're entering a storm cycle,  and if you're going out in the mountains in the next few days, it's time for a mindset shift from the spring conditions we've had recently. There may only be a few inches of new snow for Monday, but forecasts are calling for about a foot on Tuesday, and all of a sudden we're back to full-on winter. 

We'll get an inch or two of snow at upper elevations Sunday night, but precipitation will probably be rain at mid and lower elevations except for an inch or two later in the day. At the start of the day, snow could be wet and sloppy up through mid elevations. This might mean that when temperatures cool, and snow starts falling at mid elevations and the top of lower elevations, it could bond well to the underlying wet layer- but you'll have to investigate as the storm progresses to see how well the new snow is bonded. 

Monday is the major cooling day, and there could be lingering wet snow problems at mid and lower elevations, like triggering small wet slides as the rain further saturates the snowpack, glides, or cornice fall. If you easily sink through softened surface crusts, to your knees or deeper, stay away from steep slopes on Monday. An observer in the Baker backcountry on Sunday reported a poor surface freeze the night before, and sticky snow surfaces. They saw plenty of small glide cracks, but none appeared to have slid in recent days. 

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