Boletín de aludes

West Slopes North

Northwest Avalanche Center
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Peligro de aludes

Thu
Alta montaña
4 · Fuerte
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó last year. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Heavy snowfall and wind loading will push a layered snowpack to the breaking point. By Wednesday, avalanches involving weaker interfaces will not be manageable. Stick to simple, lower-angle terrain and smaller features, and avoid exposure to large slopes where avalanches can start, stop, or run.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Very Likely
    Tamaño
    1.5–2.5

    Surprising avalanches were easy to trigger on Tuesday, but they were relatively shallow. The same reactive interfaces remain in play on Wednesday. With another 12-18" of snowfall over the next 24 hours, these avalanches will be large and very difficult to manage. Slopes loading up with intense snow transport off consistent S winds will produce the largest and most lethal avalanches. Any avalanche could break widely across terrain features, and you may be able to trigger them from near or under a steep. Wednesday is a day stick to simple slopes less than 35 degrees, limiting your exposure to avalanche paths from above. Keep a wide buffer between yourself and actively wind-loading terrain. 

    (3/11/2025)

    Natural 6-8" slab that propagated 500 ft horizontally in wind loaded terrain. N aspect, 4500 ft. D1.5. Avalanches like this will be significantly deeper and more destructive on Wednesday.

    Photo: Matt Lubar

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    We received a number of reports of human-triggered avalanches in Canyon Creek on Monday that highlight a buried surface hoar interface that should be on your radar. Surface hoar that was widespread on the snow surface prior to the recent storm cycle has survived and was buried in that subzone. Other subzones like the Baker BC  and Schriebers/Mt. Baker NRA saw plenty of traffic with none like these reported as of Monday evening. Some propagated widely or were triggered from the side or below. Although the initial round of reactivity wasn't especially deep, perhaps 1-2 ft below the snow surface, we expect crowns to be 2-3 ft by Wednesday. This would produce large and difficult-to-survive avalanches on steep, open slopes. Be prepared to check the 3/8 interface, likely a few inches above a hard crust down 20" in canyon creek as of Tuesday. In areas that might have this problem, natural or human-triggered storm slabs could step down to this layer. Stay well out from under large NW-N-NE facing slopes.

     

    (3/10/2025)

    A snowmobile triggered avalanche on a northerly, upper elevation slope in Canyon Creek. Note the crown wrapping around the convex feature. This is suspected as having failed in a layer of surface hoar buried on Saturday.

    (SS-D1.5-AM-I)

     

Avalanche Discussion

It snowed more and the interfaces were more reactive than we expected on Tuesday. Shallow avalanches were a dime a dozen in the Baker Backcountry with several large avalanches (crowns up to 20") in wind loaded terrain. Most of the activity occurred on an interface buried 3/10 involving some partially faceted snow. Other avalanches involved only the storm snow that fell heavily on Tuesday morning. In some cases, the slabs ran down to the 3/9 interface. Most of the activity occurred on wind-loaded slopes. Some were natural, and many were human triggered, including from below. One avalanche triggered from below covered someone's skis and boots on the uptrack. 

We suspect that these interfaces will gradually gain strength, so we don't expect to see the number of avalanches we saw on Tuesday, but it's not out of the question. With 12-18" of snow arriving over the next 24 hours, the avalanches that do occur will be far more dangerous. The new snow is also likely to generate fresh instabilities associated with high snowfall rates and intense wind loading.  The overlapping storm slab, wind loading, and potential for more concerning layers just above the Atmospheric River (crust) crust should reinforce your conservative terrain selection.

On Tuesday, in the Baker Backcountry, the snowpack above the AR crust consisted of  8-16" of low-density snow atop 8-16" of snow that increased in density and transitioned to melt forms. There are no layers of concern below the AR crust.

We're well into a multi-day avalanche cycle in the West North. Several very large naturals likely released overnight Sunday and were observed to have run from high on Shuksan Arm and on Shuksan proper, down to the valley bottom. These likely involved wet snow.

 

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