Bulletin d’avalanche

West Slopes South

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

Particularly dangerous avalanche conditions exist due to several days of above-freezing temperatures. Natural avalanches could occur as wet snow sheds from steep faces. Look for ways to minimize or totally eliminate traveling on or under steep open slopes.

Problèmes avalancheux

  • Loose Wet

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

    You’ll certainly see loose wet avalanches on Sunday. Most of them will only entrain the surface snow and stay relatively small. You could trigger these on steep slopes, or they may occur naturally as blobs of snow fall from rocky faces or trees. A poorly frozen surface could help limit this issue first thing in the morning, but it will quickly melt, allowing for additional avalanches. 

    As the upper snowpack gets wetter and weaker we could see some of these slides gouge into older snow, grow much larger, and travel far down the slope. This version of wet loose slides is much scarier and harder to predict. These avalanches are most likely in large, rocky terrain. Give these areas a wide berth. 

    Similarly, snow could shed from rocky faces, cornices may collapse, and these slides could trigger avalanches on the slopes below. These shed-style events are hard to predict, and you don’t want to be underneath them if they occur.

    (3/16/2024)

    Large natural wet avalanches in the Crystal Lakes Basin on Saturday 3/16. 

    Photo: Crystal Mt Ski Patrol

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    You’re not likely to trigger one of these deeper slab avalanches, but they could release as smaller wet slides impact the slopes. Call them persistent slabs, call them wet slabs, it doesn’t matter. They will be 3-6 ft deep, very wide, and likely unsurvivable. 

    Recognize that any time you spend in large open terrain is a gamble, and the consequences could be dire. Look for routes that help you stay out of these paths. That includes runouts at lower elevations.

    (3/16/2024)

    Snowmobilers triggered this avalanche on a southern aspect in the Ahtanum on Saturday, March 16th. It likely failed and ran on the Early February Crust. This area is not far from the Cascade Crest (White Pass and Crystal). 

Avalanche Discussion

Forecasting wet avalanche cycles like this may be the hardest thing we do. On one level, it’s simple. It’s very hot, the snowpack is winter-like, and natural avalanches have and will occur. When, where, what type, and how big these slides will be is nearly impossible to pin down. That makes wet avalanche cycles like this very tricky to manage as a backcountry traveler. There is no simple observation. The only tool you have is avoidance. 

Saturday night will be the third in a row above freezing. This is often a benchmark for us when we start to look for the mountains to fall apart. Additionally, Sunday will be a full-notch warmer, with temperatures easily reaching into the 50s at middle elevations. With much lighter winds, it will certainly feel much hotter. 

Beneath the surface, a drier layered snowpack still exists. This includes facets on and just above the Early February Crust. A few wet slab avalanches occurred on this layer in the nearby East South zone on Saturday. They are deeper in the West South and may take longer for water to reach them. 

So far, most of the avalanche activity in the zone has been limited to small wet loose slides. However, Crystal Mt Ski Patrol noted a pair of larger wet avalanches in east facing terrain outside of the ski area Saturday morning. 

This multi-day cycle isn’t finished yet, and only time will tell when the peak danger occurred. 

Régions couvertes