Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Pay attention to changing conditions as a storm impacts the West North zone and adjust your terrain selection accordingly. Increasing winds will quickly build fresh wind slabs on lee open slopes. Rising snow levels will increase the likelihood of wet loose avalanches at low and later on in the day, mid-elevations.   

Problemi valanghivi

  • Wind Slabs

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

    This portion of the storm may bring more wind than snow.  Expect strong southerly winds to easily move new and recent snow on Friday, building new wind slabs on lee slopes at mid and upper elevations. Deeper and potentially more reactive slabs are likely at upper elevations that are well above the rain/snow line where denser slabs build over weak older snow (see gallery).  

    The usual red flags for developing wind slabs like blowing snow, textured snow surfaces, firmer or hollow-sounding snow, and shooting cracks will point you away from nearby steep open slopes below ridgelines and towards more sheltered and lower angle terrain.  

    (3/2/2024)

    If you see or trigger shallow wind slabs in wind-drifted snow like this one from earlier in the week, you know hazard it's time to avoid similar nearby slopes.

    Mt Herman, SW @ 5100'.

    Photo: Kameron Decker Harris

  • Loose Wet

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

    The rain-line is expected to start low and gradually rise to near 5000' on Friday afternoon although there's a fair amount of uncertainty regarding how much precipitation will fall in the West North zone.  Plan for a few inches of wind driven snow changing to rain at lower and mid-elevations as snow levels rise during the day.  New and recent low density snow will be primed to slide downhill as temperatures warm and rain changes to snow.  Most wet loose avalanches will be small, but some may become large, especially on shadier aspects that are holding colder, looser snow heading into this storm (see gallery). 

    At elevations where the snow becomes heavier, you experience a transition to rain, or see pinwheels/natural wet loose avalanches, it's time to avoid being on or under very steep slopes, especially slopes with terrain traps like cliffs, dense trees or gullies. 

    (3/7/2024)

    Wet loose avalanche activity that has been confined to steeper southerly aspects mid-week should now expand around the compass on Friday. 

    Photo: Julz Holder - Grouding Truth

Avalanche Discussion

Since our memorable storm and avalanche cycle at the end of February, conditions have stabilized and few avalanches have been observed over last few days.  During periods of better visibiltiy, you could pick out partially filled in large to very large crowns from natural avalanches down to the Early February or 2/24 crust, but since then, only shallow wind slabs and more recently, small wet loose avalanches were noted.  The western part of the zone experienced a mix of sun and clouds Thursday, keeping small wet loose avalanches localized to a few steep southerly slopes.  Forecasters found a generally stable snowpack and weak snow grains well preserved in the top few inches. 

Also on a positive note, backcountry travelers have found the deep recent storm snow has been settling, and the risk associated with deep snow hazards are decreasing.  There are still tree wells and holes to contend with but it's a different upper snowpack than just a few days ago. 

The early February crust varies from 6-12'(!) down across the zone.  Even as we enter a more active weather pattern, we're unlikely to see avalanches down to older layers of concern. 

 Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations HERE. 

Regioni coperte