Boletín de aludes

East Slopes North

Northwest Avalanche Center
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Peligro de aludes

Fri
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

Expect easterly and southerly winds in the early morning of Thursday on the heels of a recent west wind event. You may be able to trigger avalanches at upper elevations and in areas of wind-drifted snow. If you experience warning signs of loud collapses or cracks shooting through the snow, stick to lower-angle slopes, under 35 degrees.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Signs of these avalanches include blowing snow and stiffer snow near the surface or in the upper snowpack. Steer around thicker pillows of drifted snow on steep slopes. Watch out if you find punchy, softer layers underneath. Keep an eye out for "red flag" warning signs like shooting cracks or whumphing collapses. If you find any of these clues, move to lower-angled slopes, windward terrain, or lower elevations. Expect another burst of south and east wind overnight and into Thursday morning. Observers in the Hairpin valley reported that westerly winds formed slabs and stiffened snow surfaces on Tuesday into Wednesday. 

    If you trigger these avalanches, they may be big enough to injure you. Less likely, but very dangerous, would be triggering older, deeper drifted slabs that rest on facets in the lower half to third of the snowpack. The resulting avalanche could be big enough to kill you. While this structure may be isolated, I found it on Saturday after being surprised by a large collapse around 7,600ft on a southwest aspect near the Highway 20 hairpin, just east of Washington Pass.

    (12/3/2022)

    Very shallow 2-3" chunks of wind slabs could be initiated on kickturns above treeline. Hairpin valley, SW, 7,500ft.

    Photo: Josh Hirshberg

Avalanche Discussion

Crusts exist on steep south slopes. Surface hoar grew large and widespread. While it may have been blown over by wind, look for it on or just under the surface of wind-sheltered slopes

While unlikely, you may be able to trigger avalanches in steep open terrain at low elevations, near valley bottoms, or east of about Mazama where the snowpack remains shallow. On Monday, I traveled just north of Mazama. Snowpack tests were easy and impressively reactive with propagation where I found older drifted slabs. We felt a few small collapses while approaching the profile site on a low, broad ridge. Another observer in the areas reported collapses in open terrain below treeline and one at as high as 6750ft. Cold temperatures and shallow snow have kept the snowpack in the eastern mountains weak. 

You can find the mid-November facets (buried 11/22) just below the middle of the snowpack on most slopes from Washington Pass into the eastern mountains. It's uncertain if they remain intact as far west as Rainy Pass. We haven't received reports of avalanches on this layer, but it's been the source of numerous reports of collapsing, mostly at lower elevations. The grains appear to be bigger and "sharper" further east. Near and west of Washington Pass and below about 7,000ft the facets received rain and you'll find them just under a crumbly crust. The overlying snowpack also varies from east to west and with elevation. It's generally deeper as you move west and higher in elevation. Overall, the weak layer seems most problematic where the grains are the biggest, closer to the surface, and have a stiffer slab immediately on top. Big future storms could bring avalanches to areas where the weak layer is well-developed.

The winter is off to a great start. It's tough to remember that it's only early December. There are still many parts of the mountains where we don't have information. Be ready to make your own assessments of the snow and avalanche conditions and let us know what you see by submitting observations.

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