Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Heavy snowfall overnight and into Sunday will increase avalanche danger at all elevations. Stick to sheltered, lower-angled terrain and limit exposure to big slopes overhead. If you see widespread signs of instability or naturally triggered avalanches, assume High avalanche danger and avoid traveling on or under all steep terrain.

Problèmes avalancheux

  • Storm Slabs

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

    It won’t be the day to tip-toe around the avalanche problem. In addition to the increasing likelihood of human and naturally triggered avalanches, weather conditions should make navigating and assessing avalanche terrain quite difficult. Expect heavy snowfall and strong winds to persist for much of the day.

    You are more likely to trigger an avalanche on wind-loaded slopes. But consider all steep slopes as suspect given the amount of new snow in the forecast and the possibility it’s loading layers of buried surface hoar and weak facets. Don't ignore signs of instability like whumphing or shooting cracks. When in doubt, stay on slopes too low in angle to slide

    (1/18/2024)

    Small avalanches on features like this gully wall are a good sign you can trigger a larger avalanche on a bigger slope.

    Photo: Irene Henninger

Avalanche Discussion

NWAC is devastated to report the death of one of our Avalanche Forecasters, Matt Primomo. Tragically, Matt passed away in a non-avalanche accident away from work on Thursday, March 7th. Matt has been a key member of the NWAC family since 2017. His life in the mountains touched so many people. We are absolutely heartbroken. Please join us as we mourn this immense loss with Matt’s family, friends, and community.

Discussion: 

You could see rollerballs and small wet avalanches at lower and even mid-elevations if snow levels are slightly higher than forecast.  Natural wet loose avalanches tend to initiate in cliffy or treed terrain. You can also get wet snow moving downhill with you when descending steep slopes. Lower elevations may not be significantly safer if it’s raining or the snow is wet and mushy.

Besides fresh slabs of new and wind-drifted snow, the main factor affecting stability going into the weekend is how much surface hoar survived the first round of wind and increasing temperatures. A layer of surface hoar buried about a foot deep was found in the Baker BC in wind-sheltered, northerly terrain. It repeatedly produced propagation in testing. While this is only one observation, it also confirms that buried surface hoar can be found in terrain with certain characteristics - mid-elevation, shaded slopes where the surface hoar didn’t melt and the wind didn’t blow it away.

On Saturday, observers in the Baker BC reported marginal visibility, strong winds, and fresh, reactive wind slabs on leeward aspects. While none of the reported wind slabs were bigger than D1, difficult travel likely kept most people out of the kind of terrain where they could trigger anything bigger. A thin but crunchy rain crust was found on all aspects up to and above 4500’.

There is anywhere from 4-12’ of snow over the Early February Crust depending on aspect, elevation, and exposure to wind and sun. Forecast zones to the east and north have seen continued avalanche activity at this or other weak interfaces slightly higher in the snowpack. West North mostly escaped dealing with it other than widespread natural and control work triggered avalanches during and immediately after the biggest storm from February 28th to March 1st. Those many feet of snow have been observed as well-settled, right-side-up in structure, and have no layers of concern.

Régions couvertes