Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Another day of warming and sunshine will maintain concern for wet loose avalanches. Watch for changing conditions throughout the day and move to shaded or lower angle terrain by the time snow surfaces become wet and weak. Travel cautiously at upper elevations where you can still trigger an avalanche in wind drifted snow on slopes 35 degrees and steeper. 

Problèmes avalancheux

  • Loose Wet

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

    The loose wet cycle will continue Monday with another round of warming and strong sunshine. Wet loose activity was widespread in neighboring zones on Sunday, but generally small. More sun-exposed slopes will shed snow Monday, and a significant spring thaw will continue through the week. 

    The day will start out cold, but expect snow to begin melting off trees and rocks by mid-morning. Falling snow on slopes below may be first to initiate loose wet avalanches. The sun will work around the compass as the day progresses, and wet loose avalanches could occur on any steep slopes in direct sun. 

    Pay attention to rapid changes in the snow surface, rollerballs, and avalanches on similar slopes. It's time to move to shady slopes or head home early when you start noticing these indicators. Keep your return routes in mind as well - slopes you crossed safely early in the day may become wet, weak, and dangerous by afternoon.  

    (4/9/2021) Recent large wet loose avalanches on steep southeast aspects on Lichtenberg in the Stevens Pass Zone.

  • Wind Slabs

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

    Above 4000ft, 12-16in of settled snow from recent storms (4/7-8 and 4/9-10) is generally well bonded to an underlying crust (4/7 interface). Evidence of wind-affected snow is easy to find in the alpine. Some concern for wind slabs lingers, but these slabs are a few days old and gaining strength. You may still find unstable areas of wind drifted snow at upper elevations, primarily on north and east aspects above 5000ft. The most likely places to trigger an avalanche in wind drifted snow would be on rollovers 35 degrees and steeper, and on slopes below cornices and cliff bands. Use visual clues to identify and avoid wind-loaded snow in consequential terrain. Use test slopes and hand pits to assess how recent snow is bonding to old snow surfaces looking for sudden or easy failures. Recent avalanches, cracking, and collapsing are clear signs of unstable snow and should direct you to lower-angle terrain. 

    (4/11/2021) A small snowmobile-triggered wind slab (D1) on an east aspect at 5000ft near Park Butte in the Mt. Baker NRA in the West North Zone.

Avalanche Discussion

On Saturday, a skier triggered an avalanche in the Snoqualmie Pass Zone and was caught, carried, and fully buried. Fortunately, the skier was rescued by their partner and survived, but sustained injuries during the event (Accident Summary, Video). Several other near misses occurred over the past week throughout the region including catch and carries in upper elevation terrain and close encounters with large natural glide avalanches.

Observers in adjacent zones reported numerous small wet loose avalanches on Sunday and a handful of small human-triggered wind slabs in steep alpine terrain. Sunny spring weather looks to continue for several days, and the wet loose cycle has yet to run its course. Wind slabs are becoming harder to trigger, but stay alert as you climb up in elevation and transition into wind-affected terrain. Expect a mix of wet and dry snow problems and big variations between aspects, elevations, and time of day.

Continue to identify and avoid cornices. They grew large throughout the winter and will be tested by sun and warming on Monday. Stand far back from these features along ridges, and avoid travel on slopes below. Plenty of glide avalanches occurred over the past week as well. Keep your eyes peeled for crevasse-like cracks in the snowpack and avoid travel on or below slopes where they exist.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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