Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Fri
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2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Numerous wind slab avalanches - natural and human triggered - were reported Wednesday. Look for and avoid steep terrain features holding recently wind drifted snow. Heavier snow showers in some areas could create shallow, unstable slabs on all aspects in the afternoon.

Problemi valanghivi

  • Wind Slabs

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

    Wind slab avalanches were reported from multiple areas of West North. These will gain strength and become more difficult to trigger Thursday but they still pose some hazard, especially in consequential terrain. You might find easy to trigger slab avalanches on all aspects where there are heavy snow showers Thursday afternoon.

    If you trigger a slab avalanche Monday it would likely be on a downwind slope just below ridgeline or on terrain features like convex rollovers, gully walls, or around cliffs and rock outcroppings. Look for blowing snow, changes in snow consistency, or visual clues like cornices and wind-scoured ridgelines to identify areas of wind slab

    Test slopes and hand pits can help you monitor differences in layering as you change aspects and gain elevation. Evaluate the bond of wind slabs and ease into steeper terrain - or just find a lower-angled line around areas like convex rolls where you are more likely to trigger one.

    (4/12/2023)

    Small human triggered slab avalanche in wind loaded terrain on Shuksan Arm. North aspect at 5400'.

    Photo: Adam Ü

Avalanche Discussion

The amount of wet loose avalanche activity Wednesday varied across the zone. Some areas like Schriebers saw a rapid cloud build-up that limited warming. Other areas like Canyon Creek and the Baker BC saw more consistent sun and the resulting wet loose avalanches on southerly aspects. More clouds are forecast for Thursday but you could still see wet avalanches, especially in the morning. Keep track of what’s going on above you and be ready to adjust your plan anytime it starts to warm up.

Wednesday brought sun, powder snow, and good visibility to observe both recent avalanches and also those from the storm and rain event on Sunday. The latest 12”-16” of new snow was redistributed into wind slabs, mostly likely during a period of stronger winds Tuesday morning. Numerous natural slab avalanches - most D1.5 or less -  were found in Canyon Creek with fewer in the Baker BC and Schriebers. Human triggered wind slabs were less in number but still reported from most well traveled areas within West North and also from the Mountain Loop in West Central. Many wind loaded areas still held soft snow versus stiff wind slab. A handful of very large avalanches (D2.5-3) were also reported. Most of these are suspected of releasing during the last big storm and rain event.

Solar aspects should have some sort of crust for the rest of the week while shaded aspects hold excellent snow. Below the most recent snow, the upper snowpack structure is comprised of dense rounded grains separated by melt-freeze crusts formed by rain and sun. While it is unlikely a person could trigger a slab avalanche below the old-new snow interface, larger avalanches out there show us that deeper layers can always wake up with heavy loads of new snow, rain, or big triggers like cornice fall or a smaller avalanche.

 

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