Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Westerly winds will increase on Tuesday afternoon and could be strong enough to form 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.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    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 will increase on Tuesday afternoon and there's still soft snow available to blow around and form new slabs. Any recent wind slab avalanche would likely be a small, shallow pocket of snow. These avalanches may be just 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. 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

While unlikely, you may be able to trigger avalanches in steep open terrain at low elevations, near valley bottoms, or east of about Mazama. Cold temperatures and shallow snow have kept the snowpack weak. Many observers have reported large collapses in these areas, though no avalanches. Possibly because there's minimal cohesive slab overlying the weak layer. 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. It's possible that a big load of snow could bring avalanches to these areas with shallower coverage.

Over the past 3 days, the sun and warming temperatures formed crusts and small rollerballs on steep, sunny slopes, especially at mid to upper elevations and above valley bottoms. 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.

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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