Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 7 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Get ready for a wet and windy day. Avoid travel directly beneath cornices, glide cracks, and slopes showing fresh wet avalanche activity. Steer around steep terrain holding freshly wind-drifted snow at upper elevations. Stormy conditions will likely limit how high most people get in the mountains on Saturday.

Problèmes avalancheux

  • Wind Slabs

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

    Heavy snowfall and strong winds through the day should form fresh slabs. The slabs of moist new snow will probably be stubborn to trigger, but with stormy conditions and bad visibility, they won’t be something you want to mess with in steep, upper elevation terrain. If snow levels are lower than forecast, wind slabs could also start forming at mid elevations.

    Blowing and drifting snow should show you which slopes are loading up if you do make it up high. Cornices and scoured slopes can help you identify wind-loaded terrain after the wind stops blowing. You are most likely to trigger a wind slab during or immediately after its formation.

    (3/12/2022)

    Blowing snow is the most obvious sign that wind slabs could be forming on leeward slopes.

  • Glide Cracks

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

    The biggest concern on Saturday is probably not widespread wet loose avalanche activity, but an isolated, high-consequence release of a cornice, glide slab, or block of snow shedding from a cliff. Even a small chunk of snow falling from above can entrain saturated snow on the slope below, and turn into a decent-sized avalanche by the time it hits the runout.

    Many low-elevation areas have thin, patchy snow cover, but if you’re traveling on snow at low elevations, use the same caution you would at mid elevations. Identify overhead hazards and limit your time beneath them. If you make it just above the rain–snow line, you may also see fresh rollerballs and trigger small amounts of wet new snow on steep slopes.

    (12/21/2023)

    A thin and wet snowpack is breaking and gliding on this steep, vegetated surface in the Baker backcountry.  

    Photo: Andy Harrington

Avalanche Discussion

It might seem ironic to say that 5000-foot temperatures cooled to the upper 40s and low 50s on Friday, but that’s the case after highs over 60 degrees the day before. No fresh wet avalanche activity has been reported in the past few days, though observations have also been limited as many users appear to have shifted away from snowy mountain travel. Highway 542 past Glacier has also been closed for the entire week. Fewer reports likely reflect fewer people in the mountains, not necessarily a complete lack of avalanche activity.

The upper snowpack above the late-January crust consists mainly of moist melt-form grains, with more developed melt-forms below the crust. In alpine terrain, pockets of dry snow remain beneath the late-January crust, and snow surfaces have partially refrozen during clear nights. Supportable spring-snow conditions have been found at upper elevations, generally above 6000–7000 feet. Snowpack settlement has largely stalled despite well-above-normal temperatures. This suggests the snowpack has already undergone a major transition due to rainfall and melting, and will likely tolerate the forecast inch or so of rain at low and mid elevations.

Régions couvertes