Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

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

Points saillants

Continued stormy weather should maintain dangerous avalanche conditions throughout the West South zone on Friday. Give the snowpack time to adjust to the recent inputs by avoiding slopes over 35 degrees. Expect to find deeper storm totals and even more wind effect if you’re on a volcano.

Problèmes avalancheux

  • Wind Slabs

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

    You’ll likely need to manage Wind Slabs on Friday near ridgelines, the base of cliffs, confined chutes, or on convex slopes over 35 degrees. These slabs should be larger and more reactive as you ascend in elevation or on the volcanoes where more snow has fallen. Fresh cornices that look sharp, textured surfaces, or new drifts behind objects are visual clues you can use to determine wind-loaded aspects. Once you know which way the wind was blowing, look for smooth “pillow-like” piles of snow that appear “fat” or feel stiffer compared to the surrounding snow to identify Wind Slabs. Using small test slopes or uptrack tests as you travel can give you clues about how wind-drifted snow is reacting to your weight as a traveler. If you suspect a slope to be wind-loaded, best to avoid it at this time.

    In wind-sheltered areas, there’s still a chance you could encounter reactive slabs on slopes over 35 degrees. Use your test slopes and uptrack tests to look for cracking and failing of the snow as mentioned above. Additionally, you can use small hand pits as you travel to look for failure points in the recent storm snow. If you find that snow is cracking or failing easily in blocks during your tests, avoid slopes over 35 degrees.

Avalanche Discussion

Snow and wind are expected to continue on Friday throughout the West South zone, with a higher focus on the volcanoes, specifically Mount St. Helens and Mount Rainier. Generally speaking, we should see a decrease in precipitation intensities along with wind speed compared to what was experienced on Thursday where winds hit 70 mph in the zone and anywhere from 6-10 inches of snow fell.

Observations from Thursday are fairly limited, but avalanche professionals in the Crystal Mountain area reported fairly low-density snow over a subtle crust, with pockets of unstable snow failing on small test slopes. Further south along the crest, reports from White Pass indicate lots of blowing snow and active Wind Slab formation. Again, pockets of wind-drifted snow were easy to trigger by skiers on small test slopes. 

Prior to the storm widespread weak surface hoar was reported and a thin sun crust formed on Wednesday afternoon on slopes that see direct sunshine. These prior surfaces could mean a poor bond has formed at the new/old interface and could result in some surprising avalanches breaking above you or spanning far distances. Combined with fluctuating freezing levels, strong winds, and a less than steller bond deeper in the snowpack at the 2/25 interface - there are numerous potential points of failure in the upper snowpack that you should investigate before committing to a slope. You should also be aware of freshly formed cornices, they will likely be sensitive and could fail easily.

Régions couvertes