Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Warming temperatures and strong solar radiation will create wet loose avalanches on sun-exposed slopes. Monitor changing conditions throughout the day and move off steep terrain where dry snow is becoming wet. If you venture into the alpine, use visual clues to identify and avoid wind-loaded slopes greater than 35 degrees.

Problemi valanghivi

  • Loose Wet

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

    Expect cool overnight temperatures with a day of clear, sunny weather Monday. Widespread wet loose activity could occur on steep sun-exposed slopes as it warms up throughout the day.  Avalanches will likely just involve new snow from Saturday night's storm, and should mostly be small. On big sunny slopes at upper elevations, wet loose slides could run further, entrain more snow, and could even grow large. Watch for rapid changes in the snow surface, rollerballs, and avalanches on similar slopes. It's time to leave and head for shady slopes, or lower-angle terrain when you start noticing these indicators. 

    (3/27/2021) Example photo of a small natural wet loose avalanche on a sun-exposed slope in the Mt. Baker Backcountry. Photo: Zack McGill

  • Wind Slabs

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

    Saturday night's storm brought 4-6in of new snow above 4000ft. The storm came in warm and wet before temperatures dropped as precipitation ended. Slabs of wind drifted snow may still be reactive to human triggers on leeward upper-elevation slopes 35 degrees and steeper. Unstable snow will be easiest to find close to ridgelines, or at the top of alpine start zones. Test the sensitivity of new snow/old snow interface before committing to consequential slopes. Cracking, collapsing, and recent avalanches should direct you to lower-angle terrain. 

    Example photo of a test slope that cracked easily under the weight of a ski. Cracks like this are a good sign that you can trigger avalanches on wind-loaded slopes. 

Avalanche Discussion

Heavy rain came Saturday night before precipitation transitioned to snow. The rain saturated the upper snowpack to at least 5000ft, and new snow is generally well bonded to old snow surfaces. Observers in the Baker backcountry on Sunday reported shallow wind slabs on leeward alpine slopes, large cornices, and evidence of isolated glide avalanche activity. Clearing skies and sunshine affected snow surfaces in the afternoon with minor wet loose activity just beginning. The new snow was a nice refresh and riding conditions were good.

Continue to stay alert during the ongoing transition from winter to spring.  Cornices grew large over the past few months and loom along many high elevation ridgelines. Take them seriously and be cautious along ridgelines and in cornice run-out zones. We've seen large glide avalanches in other zones. Widening glide cracks and glide avalanches have been observed throughout the West North Zone over the past few weeks. Limit your time below open glide cracks and/or cliff faces that continue to hold snow. 

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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