Boletín de aludes

Stevens Pass

Northwest Avalanche Center
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Peligro de aludes

Sun
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

A couple inches of snow will fall with moderate to strong winds on Saturday, which may slightly increase your avalanche concerns, especially near and above treeline where wind has more effect. New drifts of snow will form, and these slabs could avalanche with a human trigger, which is important to pay attention to as the day progresses and more snow falls. You could also trigger a large persistent slab avalanche, and for both of these problems your best way to manage them is so steer around steep, wind loaded terrain, where you'll still probably be able to find nice snow.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2

    Recently formed wind slabs may easily be triggered in certain areas.  They could form just deep enough to slide - a few inches deep, to 6 or more inches, in the new snow from Saturday. This is especially the case as a small but intense burst of snow arrives with strong winds midday. Reactive slabs could be deeper, as wind has consistently redistributed snow in recent days.  The distribution of slabs may be patchy, but they may be easy to trigger. Reports from Friday indicated a weak interface at the snow surface. Check to see how the snow reacts on small test slopes. Look for punchier deeper drifts, cornices, and textured snow surfaces to identify likely slabs.  Steer around steeper slopes if you find shooting cracks, or thick slabs in large terrain features where getting caught in a slide could be less than ideal. 

    (1/19/2023)

    Shallow snowboard triggered windslab on windward slope of Lichtenberg on 1/19.

    Photo: Nate H-S

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–2.5

    On Thursday, the third skier on a slope triggered a large and surprising slab 1-2ft deep on a NE aspect at 6,200ft. It ran on large surface hoar on a firm bed surface, triggered from a shallower area. This was an indicator that we do still have a persistent slab problem. The slide even broke through the MLK crust which was about 5mm thick in this location. 

    It's important to rethink how you travel with these dangerous avalanches in mind. You're most likely to trigger one of these large avalanches on N-E aspects above 6,000ft, on the east side of the pass. Treat steep slopes that fit this description with a large amount of skepticism. You could dig down and look for feathery surface hoar about 2ft deep near a crust. Unfortunately, distribution is variable throughout like aspects and elevations, so even if you don't find the weak layer/crust interface in one place, that doesn't mean it's not hiding out in another.  

    (1/19/2023)

    Large avalanche on a layer of buried surface hoar. NE at 6,200ft on Jim Hill. The crown was 1-2ft deep.

    Photo: Ryan Minton

Avalanche Discussion

Steep slopes facing south may have a thin crust on them from Friday's sunny skies. Given the persistent slab problem and where it exists, keep in mind that triggering a shallower wind slab avalanche could add enough weight to cause an avalanche to step down to the persistent weak layer. Keep the unexpected persistent slab avalanche which occurred and our subsequent concerns a focal point for planning your day in the mountains. It was a surprise to the experienced folks who triggered it and to those of us who thought this was no longer a concern in the area.  It's a testament to how tricky our snowpack has become in the Cascades at the moment. Don't let yourself get surprised out there, we now have this relatively recent bullseye information regarding a persistent weak layer.

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