Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Heavy snow and strong winds are expected to create very dangerous avalanche conditions. Stay off of, and out from underneath steep slopes because avalanches may be triggered easily and run naturally. Slides could step down to a buried crust, become very large and run to valley bottoms.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    Saturday is not a great day to venture into or underneath avalanche terrain. The storm snow will be falling on a variety of weak surfaces, mostly low-density snow. Rapidly accumulating new snow may easily overload these weaker, existing surfaces, and warming temperatures in the atmosphere may create strong over weak layering. Any avalanche in the new snow could step down to deeper weak layers and become an unsurvivable slide. Stay off of, and out from underneath steep slopes on Saturday because large to very large avalanches are expected to be easily triggered and can run naturally.

    Observers have noted sudden failures on a crust about 3ft down, and at least one deeper avalanche that we know of ran on this layer last weekend. On upper elevation terrain and wind-loaded areas, the storm load may be enough to tip this layer over the edge and create deeper and more destructive avalanches. Be sure to consider what is above you before riding underneath large avalanche paths. If you venture out, look for bullseye data such as recent avalanches and shooting cracks to inform you that the snowpack is unstable, and avalanches are likely. 

    (12/12/2021)

    A natural avalanche above Blue Lake likely ran on 12/11/2021. Washington Pass

    Photo: Josh Cole

Avalanche Discussion

By the time morning hits, the storm should be well underway. Accumulations of 1.5-2ft of new snow are a good bet by the end of the day.

Over the past couple of days, avalanche professionals north of the border have noted an increase in avalanches on a crust that was buried in early December, despite fairly benign weather. This up-tick in activity should give us pause, especially because the same facet/crust layer exists in this zone. You can find it anywhere from 1-3ft down from the snow surface in the Washington Pass area, depending on elevation and proximity to the west. Observers have found snowpack tests that indicate consistent propagation, and heard whumphing collapses in the Washington Pass area. All of this speaks to the potential for much larger and surprising avalanches to occur with the storm this weekend. 

During the week, the winds picked up and may have formed slabs in unusual places. Plenty of low density, cold snow still exists on the surface and stands to be transported easily with the strong winds that are forecast. A similar storm affected the area last weekend, and it was very active near Washington Pass. Many natural avalanches up to size D2.5 were reported, and some even crossed the snowed-over highway.

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