Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

While you may encounter pockets of recent wind drifted snow, let the consequences of the much deeper and less predictable hazard shape where and how you travel. Large avalanche paths may produce big avalanches. Therefore, give large open slopes a wide berth as this persisting danger continues.

Avalanche problems

  • Wind Slabs

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

    Easterly winds on Thursday drifted snow into new and reactive slabs on some unusual aspects. By Friday, a few inches of soft snow could hide some of the more obvious signs that wind slabs exist. Instead, you’ll need to look for more subtle clues to identify slopes and features you want to avoid. When you notice drifts behind objects or find the snow feels different, use these observations to anticipate nearby wind-loaded terrain. If you suspect a wind slab exists on a feature, go around, and seek out less wind-affected or lower angled slopes. These slabs likely formed over very low density and potentially weak surface snow grains. This may allow them to trigger easily and propagate widely. With easy to trigger wind slabs on some unusual aspects, approach this common avalanche problem with a bit more caution.

    (2/11/2021) Wind drifts like these, seen on Mt Catherine Thursday (2/11), can help you anticipate wind loaded slopes.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Over the past week natural, human triggered, and explosive triggered avalanches point toward one thing: a deep persistent weak layer. While no new avalanches were reported on Thursday (so far), this is the first day in a long time without a new observation. You could travel all day, and the snowpack may “feel” safe or stable, However, the recent red-flag avalanche observations implore you to continue to give this tricky avalanche problem the respect it deserves. While several persistent weak layers exist in the snowpack, if you trigger any of them, it would result in a very large and destructive avalanche. Avoid traveling on large open start zones, particularly at mid-elevations.

    (2/10/2021) This recent natural deep slab avalanche was observed from the Denny Trees area on Wednesday. It may have been triggered by a piece of cornice from above. Low Mountain, NE, 5000' HS-N-D2.5/R2-O, Photo: Jonathon Spitzer

Avalanche Discussion

Very cold and snowy weather will maintain the avalanche danger at Snoqualmie Pass Friday. By the end of the day, you could find 4-6” or more of new snow. While you’re most likely to encounter a newly formed windslab, it’s the deeper persistent layers that weigh heavily on our minds. The snowpack seems to be entering a classic low-likelihood/high-consequence scenario. While the likelihood may appear lower, let the dire consequences shape your terrain selection. 

If you dig in the snow you may find two significant weak layers. A thin facet/crust (2/1) combination sits 3-4’ below the snow surface. Slightly deeper (4-5') the more widespread and easier to identify mid-January crust/facet layer exists. This layer failed in several recent avalanches including a very large natural in the Denny Creek drainage on Wednesday, a near-miss near Stevens Pass, a burial just east of Snoqualmie Pass, and an avalanche fatality near Salmon La Sac. (See the short video in the media gallery below for more information). The snowpack structure appears nearly identical in all of these events. You can help us track this weak layer by submitting snowpack observations on our public site. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

Regions covered