Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Stormy weather will take aim at the West South zone through Friday and create dangerous avalanche conditions primarily due to wind-loaded snow. These new slabs may trigger easily and could grow large enough to bury you. Avoid steep slopes on the wind-sheltered side of exposed ridges.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    All the ingredients are there. Very strong winds and significant snowfall should combine to form new slabs over an old crust or weak snow (bed surface). As a result, you may see some of these avalanches fail easily and run quickly. Blowing snow, sharp cornices, textured surfaces, and fresh drifts can all help you anticipate and avoid wind-loaded slopes. You’re most likely to encounter one of these firmer slabs near ridgelines, below cliffs, and in the tops of chutes. 

    As the day continues and more snow falls, these slabs could grow quite deep and dangerous. Give them a wide berth and seek out more sheltered terrain to avoid the hazard.

    (3/21/2023) Clear signs of wind loaded slopes can help you anticipate slabs. Photo: Dallas Glass

Avalanche Discussion

The West South zone is squarely in the bullseye of this storm. As of Thursday afternoon, new snow totals range from 2-3 inches at Crystal to 8-12 inches at White Pass, Paradise, and Mt St Helens. And, we’re not done yet. Expect stormy weather to continue well through Friday. Mt St Helens could see the greatest impacts with an additional 18 inches of snow. That means you may see locally very dangerous conditions with large natural avalanches in this area. 

Since we’re expecting a cooling trend with this storm, we think the main hazard will be localized to wind-loaded areas. However, in those places that see more than a foot of new snow, it could be worth easing into the terrain. Use smaller low consequence slopes to see how the snow reacts before traveling larger wind-sheltered features. 

Closer to the crest, there is a chance the sun may pop out momentarily on Friday. If it does so, this new snow will probably start to slide downhill. Expect to see rollerballs and small loose wet avalanches during short-lived sun breaks. 

Prior to this storm, spring-like weather with warm temperatures and sunshine began to alter the snowpack. A surface crust formed on E-S-W aspects high into the terrain, and onto more shaded slopes at lower elevations. However, cold dry soft snow managed to persist in northerly areas. Some of this snow may have started to weaken (facet) during this dry period. Below this old surface, we don’t have any significant layers of concern. As a result, we anticipate avalanches to fail at or above the new 3/22 interface.

Regioni coperte