Boletín de aludes

Mt Hood

Northwest Avalanche Center
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Peligro de aludes

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

Lo esencial

You can still trigger a large avalanche above treeline in places where the wind has drifted snow into thick slabs. Look for fresh cornices and wind-textured snow to help you identify which slopes to avoid.  Once the sun comes out, you may see small wet loose slides releasing on steep, solar slopes.

Problemas de aludes

  • Wind Slabs

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

    Freshly formed wind slabs will remain reactive on Tuesday, specifically above treeline.  New snow from the last 24 hours is available for transport and will continue to build the size of the existing slabs. These wind slabs are easily 1-3 ‘ thick now. You will find these areas of wind drifted snow in all the usual areas (under cornices, lee-sides of ridges, & scattered in the alpine), however you may find them further down slopes than usual and in lower elevation areas due to recent gusty winds.  

    Be wary of open slopes at mid elevations which may harbor a buried layer of surface hoar. If you trigger a wind slab in these locations, it could step down and produce a much larger and widely propagating avalanche. 

    Be observant of the snow you travel on and look for signs of recent wind loading.  Fresh cornices, wind rippled snow, pillow-like slabs are all signs of wind slabs. Steer around steep slopes if you observe these signs of wind loaded snow, see shooting cracks, or hear audible whumphs. 

    (12/3/2022) A shooting crack in a wind-loaded pocket. One of the red-flag signs of instability that shouldn't be ignored. Photo: Dallas Glass

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    A high-pressure ridge building may allow for some sunshine to develop across the zone.  This filtering sunshine will moisten snow surfaces on south-facing aspects. Much of the current surface snow is dry, so you see rollerballs and pinwheels quickly initiating  shortly after the sun hits the snow surface.  Once you start seeing these signs - that's a good time to start thinking about steering around steep south-facing slopes.  

    Once the sun hits the snow on south facing slopes, you may start seeing rollerballs and small wet loose slides like this.

Avalanche Discussion

The precipitation forecast didn’t quite materialize as we were all hoping for on Monday. However,  Mt Hood still managed to squeeze out a few inches of new snow on steady moderate winds.  On Monday,  I found wind-loaded test slopes to be reactive above 5500 ft.  It was quite windy and the new snow was actively drifting and forming sharp cornices along Pea Gravel Ridge.  These were clear signs for us to stick to more sheltered slopes below treeline. 

If the sun does make an apperence on Tuesday, it may be tempting to step out onto bigger slopes. Just remember these bigger slopes are the likely areas that you can trigger a larger avalanche in wind drifted snow.  It won't be the day to thread the needle, so carefully evatuate which slopes have a fresh slab on wind textured snow and which slopes don't.  There will be plenty more sunny days ahead...

After Saturday's report of a human triggered avalanche in the Gunsight Ridge area   (observation here), I went out on Sunday to further investigate the possible culprit - buried surface hoar.  Throughout my travels today I didn't find it everywhere, but in the places I did - it showed the ability to propagate across a slope.  Generally, I found this layer of buried surface hoar about 17 inches below the snow surface and above the 12/30 rain crust.  Check out my observation here and the photos in the gallery for more details.

Thanks for all the recent observations!

 

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