Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A powerful storm is forecast to bring heavy snow and strong winds Wednesday. Start your day with simple terrain until the storm runs its course and the new snow has time to settle. Avoid being on or under all steep slopes if you start seeing widespread natural avalanche activity. You might see signs of wet avalanches at lower elevations with midday warming and a small rise in snow levels. 

Problèmes avalancheux

  • Storm Slabs

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

    Moderate snowfall overnight should ramp up during the day and join forces with strong winds and a slight rise in snow levels. The trifecta of red flags will likely build new slabs on all aspects that are quite easy to trigger. 

    Human and naturally triggered avalanches will be more likely during periods of intense snowfall and very strong winds. Wind loaded terrain will harbor thicker slabs, but all slopes with 6" or more of new snow should be considered suspect. Don't ignore obvious signs of instability like recent avalanches and shooting cracks. If avalanches become large and widespread consider the danger rating to be a notch higher and avoid all avalanche terrain.

     

     

    If Wednesday's weather forecast pans out you could see slab avalanches like this in all terrain, not just wind loaded slopes.

    Photo: Trevor Kostanich

Avalanche Discussion

The coming storm is one that could really go either way in terms of its effect on avalanche danger. If there's slightly less snow and wind you could spend the day simply navigating around steep, wind loaded features. If it goes the other way there could be a brief but not insignificant avalanche cycle and all avalanche terrain could be off limits. Subtle changes in wind, precipitation, and temperature can have big impacts on how the day plays out. These variables affect slab reactivity (how easy to trigger), distribution (everywhere or just in a few places), and size. Be prepared to make and act on your own observations.

Non-avalanche hazards include frozen, partially buried avalanche debris, glide cracks, exposed creeks, and other natural hazards exposed by recent rain. Multiple observers out on Monday noted all of the above were greater dangers than triggering an avalanche - unless of course the avalanche pushed you into one of these traps. New snow will obviously change this equation but these day-enders will still be out there.

Tuesday was a snoozer with few people out in the mountains and even fewer observations. Mild and calm conditions are suspected of having little effect on avalanche danger other than giving dense, stubborn winds slabs even more time to bond and become unreactive. 

During the last storm on Jan 15-16th, wind gusts to the low 40’s redistributed 4-12” of new snow at all elevations. Near treeline, dense wind slabs and stiff snow were found nearly everywhere between patches of exposed rain crust and buried avalanche debris. But the slabs were generally unreactive and testing produced little in the way of results.  No new avalanches were reported other than a few wind slabs triggered by avalanche control work.

If you’re out in the mountains tomorrow, consider submitting an observation.

 

Régions couvertes