Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Expect a mild, almost dry morning with strong winds and increasing snowfall in the afternoon.  Natural avalanches will be less likely - but you can still find big avalanches at upper elevations, especially on unsupported slopes or triggered by a cornice fall or a smaller avalanche from higher on the slope. Keep track of the terrain ahead of you and also what is overhead. Another wet, wind, warm storm is forecast for Sunday.

Problemi valanghivi

  • Storm Slabs

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

    You could find two different types of slab avalanches on Saturday. At elevations well above the rain-snow line of 5000,’ there should be thick slabs of dense new snow. These quickly become stubborn to trigger under the influence of mild temperatures, but can still release on unsupported terrain features or with a large load like a smaller avalanche or cornice fall. The easiest solution to avoid these is to skip traveling on or directly under large open slopes at upper elevations.

    Renewed snowfall and steady winds will likely build new slabs as well, especially in the afternoon. These will be smaller, shallower, and easier to identify. They will also be more common in wind loaded terrain features As snow levels drop you will start finding them at elevations that saw only rain through Friday. 

    (2/8/2023)

    Small but fresh slabs could be on the menu by Satruday afternoon.

    Photo: Adam Ü

  • Glide Cracks

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

    Most mid-elevation weather stations will have recorded 36-48 hours of near or above freezing temperatures by Saturday morning, along with an inch or two of rain below 4500'-5000’. Wet avalanche activity will become less likely with a cooling trend and lighter precipitation. Glide slabs and cornices that started to come unglued during the storm could still fall down in the next few days. Limit travel directly under glide cracks or sagging cornices. Also be on the lookout for steep, snowy cliffs that show signs of instability like rollerballs or snow shedding off of rocks and trees.

    Example of a large glide avalanche on rock slab (just left of center) below Huntoon Point last winter.  Note hanging blocks, hangfire and a sagging cornice all surrounding avalanche release area.

Avalanche Discussion

Precipitation totals (and avalanche danger) varied a ton across the zone with the last storm. Snotel sites like Wells Creek and Middle Fork Nooksack saw about 1” of precipitation, mostly in the liquid form. Heather Meadows more than doubled that with  2.5” since precipitation started Thursday afternoon. About 6” of wet new snow fell at 5000’ with way more snow at upper elevations. The rain-snow line hovered around 4000’ to 4500’ most of the day.

Field observations were in short supply Thursday and Friday and it’s not a real mystery as to why. With high danger and poor visibility, observations were mostly limited to ski area avalanche control work that produced wet loose and slab avalanches up to D2 in size.  One backcountry team did manage to get out in the Baker BC Thursday and found this. Some subzones of West North like the Baker Backcountry and Shcirebers are suspected to have seen a natural avalanche cycle overnight Thursday whereas others might only have a few little wet loose avalanches to show for all the fuss about the last storm.

If you experience better visibility on Saturday let us know what you see out there!

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