Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

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

Stay off very steep slopes at lower and mid elevations where you find wet punchy snow, especially near terrain traps.  As you ascend and encounter drier snow, you may trigger slab avalanches on steep open slopes. Plan for increasing avalanche danger as wet and mild weather moves in over the weekend.

Problèmes avalancheux

  • Loose Wet

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

    With the steady drip of snow accumulating above 4000' over the last 24 hrs, we have new snow available for another round of wet loose avalanches at low and mid-elevations on Friday.  Where you you find wet and sticky snow, you may trigger wet loose avalanches on nearby slopes steeper than 40 degrees.  Most wet loose avalanches will be small, but they could be larger depending on the slope, if there's a crust to run on, and how much snow is available for entrainment.  Be mindful of triggering even a small wet loose avalanche near terrain traps; above trees like above trees, gullies, and cliffs.  

    Temperatures have hovered near or above freezing at lower elevations for almost a week without an extended refreeze.  These places are less likely to see new wet loose avalanches but could see big blocks of snow shed from steep rocky faces.  Move along and don't spend time below these features or anywhere you see glide cracks opening.  These avalanches are unpredictable and it's better to just put space between you and the potential hazard. 

    Avoid terrain where even a small avalanche would be dangerous.

    (1/19/2024) A small wet loose avalanche at low elevations on the east side of Herman.

    Photo: Jason Speer

  • Storm Slabs

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

    The snow-line has oscillated between lower and mid-elevations over the last few stormy days.  As you poke above this transitionary zone you're more likely to find dry snow , a lack of crusts in the upper snowpack and deeper drifts on lee aspects.  Step into these areas with a healthy amount of caution, we know very little about the stability of recent storm layers at upper elevations.  Clues like long-shooting cracks from your feet, whumphing, or evidence of recent avalanches are signs to avoid nearby similar slopes.  You can use small test slopes and handpits to get a sense of the upper snowpack. 

    Example photo: Human-triggered slab avalanches are possible in areas where you find dry snow.  

    Photo: Irene Henninger

Avalanche Discussion

Professionals reported a snow-line bumping between 3500-5000' on Wednesday and Thursday with several inches of new snow accumulating each day.  Small wet loose avalanches could be easily triggered in this zone, with signs of older small natural wet loose avalanches apparent at lower elevations.  Tuesday was more active with large wet loose avalanches reported in the Baker backcountry. 

The Mt Baker Ski Area triggered a very large slab avalanche with explosives on Hemispheres, with a crown 4-5 feet deep on Tuesday.  While we don't know the exact layer the slide released on, it's a reminder that deeper instabilities in the snowpack will become the main concern as we head into a wet and increasingly mild weekend.  Recently we've had a deceiving storm cycle without a signature storm.  Quietly we've had 4.5" of water recorded at Heather Meadows since the 21st, resulting in dry snow piling up at upper elevations along with the steady drumbeat of moderate southerly winds.  With rain expected to move into upper elevations over the weekend,  plan for increasing hazard and increasing likelihood of natural avalanches.   

Information is limited, especially from upper elevations.  If you make it out,  please let us know what you see by submitting an observation. 

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