Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Gusty winds should continue to move snow into thicker and potentially unstable piles for you to avoid on Monday. Look for these piles near rocks or the leeward side of ridgelines where the wind likes to sift the snow deeper. If storm totals exceed expectations, recognize that avalanche potential could also increase and you may have to adjust your travel plans. 

Avalanche problems

  • Wind Slabs

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

    Snowy and windy conditions should continue Sunday evening, leaving us more potential Wind Slabs to deal with on Monday. Slabs built over the weekend could thicken, or you could find freshly built ones. Look for these slabs to develop near rocky features such as confined gullies or the base of cliffs. They may also be lurking on convex slopes or on the leeward side of ridgelines. You can look for actively blowing snow to help identify newly building slabs, or look for visual clues such as fresh cornices, textured surfaces, or small drifts behind natural objects to help you identify where the wind has been at work recently. If you notice smooth pillow-like piles or find yourself in a deep stiffer pocket of snow, you should avoid these areas.

    (12/3/2022)

    Example: A small smooth pillow-like wind slab from earlier this winter. 

    Photo: Andy Harrington

Avalanche Discussion

Sunday’s storm was a little later to the party than expected, but the inches started to pile up as the day wore on. As of Sunday evening, we’ve estimated that the Pass has received about 4-5” of snow at mid to upper elevations. Accurate snow depths are difficult to measure due to the windy nature of this storm. Expect a few more inches to drop overnight, with higher accumulations possible if we get hit with convergence bands from both the west and southwest. 

While these snow totals may be moderate compared to Snoqualmie storm standards, the wind has been a major player as noted above. With gusts reaching the 50s, winds were easily strong enough to move around already in-place low-density snow along with the newly fallen storm snow. On Sunday, NWAC forecasters and avalanche professionals on Kendall Peak noticed active wind loading and some very shallow slabs starting to form. Looking up at the ridgeline, a steady plume of snow was present for the majority of the morning. Alpental Pro Patrol reported similar conditions and even a few wind-loaded pockets failing naturally in the waning hours of the day. 

The recent storm snow is overlaying a variety of previous surfaces (12/18 interface), some of which are weak. Sun crusts on more southerly slopes and surface hoar on more sun-sheltered slopes were found on Saturday prior to the storm. Near surface facets were found on a variety of aspects. On Sunday, some loose snow was sliding on the previous sun crust, but there was simply not enough to call these consequential avalanches at the time. As snow depths increase, keep these loose avalanches on your mind. We expect at some point in the next week we will reach a tipping point for more widespread slab avalanches as we incrementally load the 12/18. When that point is reached, the resulting slides may break in surprising ways by spanning far distances, wrapping around terrain features, or breaking above you. 

Deeper layers in the snowpack such as the 12/8 and 12/5 are still present but will be taking a back seat in our minds for the next few days until the load above them increases. While avalanches on these layers are not impossible, we believe them to be a low probability. 

Regions covered