Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
View on map

Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
Open full map
Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A break in the weather Tuesday should allow the avalanche danger to decrease slightly, however, don’t see this as a green light. Recent storms formed a somewhat complex and variable snowpack. You could still trigger avalanches large enough to kill you on steep convex rollovers, rocky terrain, or on unsupported slopes.

Avalanche problems

  • Storm Slabs

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

    Several weak layers exist within the upper snowpack that could fail and produce large avalanches Tuesday. As these layers gain strength and triggering a slide becomes more difficult, turn your attention to features where you might be more likely to cause a slide. Steep convexities, rocky and complex terrain, and unsupported slopes could produce large avalanches. 

    Over the last several days, multiple storms, fluctuating snow levels, and various types of precipitation created a layered snowpack. Unfortunately, the structure may change significantly with elevation, aspect, and proximity to the Pass with its cool easterly flow. As a result, don’t expect observations from one location or elevation to represent another. You’ll need to constantly look and check. Because of the strength and depth of some layers, small test slopes may not give you the information you need. Instead, you’ll want to dig with your hand or shovel and feel for strong (slab) over weak (weak layer). If you find a layer that fails easily steer around nearby slopes greater than 35 degrees to avoid triggering avalanches. 

    (12/19/2021)

    Using simple hand pits while you travel is a quick way to gain some information about slab potential and the depth of potential weak layers in the upper snowpack. 

    Photo: Dallas Glass

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Warming temperatures and rain Monday night could leave you with a wet snow surface at mid and lower elevations on Tuesday. While this won’t present a big hazard, don’t be surprised when you see or trigger small loose avalanches. Sticky snow and new rollerballs will likely serve as your best clues that the snow could produce these wet slides. While they should remain small, don’t let them push you into any of the numerous obstacles that still exist at lower elevations around the pass including open creeks, trees, and rocks. 

    Loose wet avalanches will be most prevalent near and west of the Pass or until the east flow finally loses out to the increasingly warmer air. Let the air temperature and precipitation type be your guide. When it feels warmer or you see rain, it’s time to think about loose wet avalanches.

    (12/20/2021) Example:  Rollerballs along caused by rain on snow Monday afternoon. Photo: Andrew Kiefer

Avalanche Discussion

As of Monday afternoon, 6-8” of heavier snow fell at Snoqualmie Pass. This new storm snow sits over much lighter and drier snow from Saturday night creating an upside-down snowpack. This new snow only adds to the somewhat complex and variable upper snowpack. We expect most avalanche actively to occur at the recent storm interface (12/20). Besides this new storm interface, avalanches and significant snowpack test results were reported over the weekend failing above (down 12-14”) and below (down 16-20”) the 12/18 crust.

For locations west of the Pass, recent rain and warmer temperatures on Tuesday may create a much wetter snowpack well into the near treeline band. You may encounter very wet and slushy snow. In at least one instance this caused a wet avalanche that ran below the snowline.

Regions covered