Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Kernpunkte

Westerly winds increased on Tuesday afternoon and may have formed new drifts of snow. You may be able to trigger avalanches at upper elevations or in areas of older wind-drifted snow in the eastern mountains. If you experience warning signs of loud collapses or cracks shooting through the snow, stick to lower-angle slopes, under 35 degrees.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Look and feel for subtle changes in the snow above treeline like 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 layer 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.

    Westerly winds likely formed new slabs with available snow on Tuesday afternoon. 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. This structure may be located in very specific to isolated areas above treeline, where drifts formed around Thanksgiving. On Saturday, I found this structure 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

Over the weekend, the sun and warming temperatures formed crusts and small rollerballs on steep, sunny slopes, especially at mid to upper elevations. Temperature inversions have kept valleys cold and warmed the high peaks. Surface hoar has grown large and widespread. The light snow in the forecast could bury this weak layer.

While unlikely, you may be able to trigger avalanches in steep open terrain at low elevations, near valley bottoms, or east of about Mazama. On Monday, I traveled just north of Mazama and found a mostly shallow, weak snowpack. Snowpack tests were reactive with propagation where I found older drifted slabs near an open ridge below treeline. We felt a few small collapses while approaching the profile site on a low, broad ridge. Another observer reported collapsing lower on the slope in open terrain. Cold temperatures and shallow snow have kept the snowpack 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, and they received some rain below about 7,000ft, near and west of Washington Pass. In these areas, you'll find the facets just under a crumbly crust. The overlying snowpack also varies 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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