Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Significant new snow fell on weak surfaces, and you can easily trigger large avalanches on Tuesday. It may be possible for avalanches to break wider and deeper than you expect. Choose conservative terrain and avoid steep slopes if you experience shooting cracks, collapsing, or observe recent avalanches.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    As of Monday afternoon, the storm has tapered off, and we are getting a brief break in the heavy precipitation. But light snow showers and moderate winds will continue into Tuesday. With 1-2 feet of snow that accumulated on very weak surfaces, it will take time for the snowpack to adjust and storm instabilities to settle. You may no longer see widespread natural activity, but you can easily trigger avalanches in steep terrain at all elevations. Our current snowpack is not typical for the  Pacific Northwest snowpack, and the possibility exists for these storm slabs to step down to deeper weak layers in the snowpack. Also, if you are traveling near ridges or in areas where the wind has deposited snow, avalanches may be larger and more dangerous.  

    Travel cautiously and avoid steep terrain, especially in areas with deep wind drifts. Use hand pits and small test slopes to observe how the new snow is bonding to the existing snow surfaces. Strong over weak layering that fails easily in hand pits or test slopes that produce shooting cracks or mini avalanches are all signs you should stick to low-angle terrain.

    (1/2/2022)

    Shooting cracks and whumpfing are red flag signs of instability and should drive you to lower angled terrain.

    Photo: Robin Pendery

Avalanche Discussion

Snow totals from Monday’s storm were impressive throughout the East Central zone. Trinity and Holden win, reporting over 20 inches of storm snow.  On average 12-16 inches accumulated near the Cascade crest and 5-10 inches in Eastern areas of the zone. A widespread natural avalanche cycle occurred during peak precipitation rates in the early morning hours of Monday.

There have been abundant observations of weak snow, surface hoar, and facets on the existing surface. Underlaying the weak snow is a mixed bag, from sun crusts and wind crusts to soft snow. As a result, adjacent slopes and slight variations in aspect may have very different snowpack conditions. We are particularly concerned about steep solar aspects with a few inches of preserved stellar snowflakes, surface hoar, and faceted crystals on top of a sun crust. There is a lot of uncertainty but keep in mind that avalanches may break farther and become larger than a typical storm slab. 

Mt. Baker, the Chair Peak basin, and Mt. Mastiff have all had avalanches on deeply buried weak layers in the snowpack. And Mission Ridge Patrol reported that an explosive triggered slab stepped down to the Solstice crust. These observations seem sporadic and inconsistent, but they indicate uncertainty with the spatial distribution of these deep weak layers. This uncertainty, along with the potentially high consequences of these very large avalanches, warrants extra caution as smaller avalanches may step down to deeper interfaces. 

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