Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Expect the avalanche danger to increase slightly in the afternoon as snowfall ramps up and the winds increase. You may trigger avalanches on features where the wind deposits snow deeper. Watch for blowing snow, to highlight which steep slopes you want to avoid.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    As the winds increase Thursday, watch for blowing snow on the ridges and peaks above you. This observation should clue you in to the increasing avalanche danger. New wind slabs may form on the sides of exposed features at any elevation. As you ascend, expect the slabs to become deeper and wider. While blowing snow can serve as your most obvious indication, changes in the depth of the soft snow or subtle drifts behind objects will also highlight wind loaded areas. Steer around steep wind affected slopes by seeking out lower angled or less wind loaded terrain.

    (2/3/2021) Small drifts formed in the recent snow on a variety of aspects. These were seen on Keechelus Ridge near the eastern border of the zone. NE 4800'

Avalanche Discussion

While a moderate/wind slab day may seem run of the mill for Snoqualmie Pass, don’t let this common forecast lull you into routine travel patterns. Two pieces make this forecast unique and may deserve a bit of added caution. 

1). Even though the avalanche danger remains moderate, expect the avalanche hazard to increase slightly during the day. If more snow arrives than expected, conditions could become dangerous before sunset. If you find more than 6” of new snow, start dialing back your terrain choices and avoid avalanche start zones. 

2). Persistent weak grains exist in the upper snowpack. Numerous observations over the past week from all over the zone highlight weak facets just above a stout 1/13 crust. This layer could sit 18-24” deep by Thursday afternoon. So far no known avalanches have occurred on this layer at the Pass. If slides fail on these weak grains, they could trigger remotely, break widely, and run quickly. Adjacent zones (East Central and West South) reported numerous persistent slab avalanches since last Wednesday (1/27). As we add more snow to this layer, our uncertainty grows. To make matters more complicated a new facet/crust layer (2/1) sits just below the surface. It failed easily and suddenly in multiple observations on Wednesday. 

Increasing danger, a higher than normal degree of uncertainty, and a weak snowpack structure all point towards a bit more caution than the danger rating and problem might normally indicate. 

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