Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
View on map

Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A major winter storm could bring the first significant avalanche cycle of the season Tuesday night into Wednesday. Expect the most dangerous conditions in the morning as steady snowfall and strong winds continue to impact the mountains. Chose simple terrain that allows you to easily identify and avoid steep open slopes where avalanches can start.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    At mid and upper elevations, strong easterly winds will drift snow into deep slabs on the lee sides of ridges, exposed features, and cross-load mid-slope gullies. This won’t be a day to try and poke around the edges of this beast. Most of these potential avalanches will grow large enough to easily bury or kill you. Unfortunately, shifting winds will make hunting out this problem particularly tricky. You may notice the wind transporting snow in the opposite direction than many drifts and cornices indicate. As a result, you should anticipate wind slabs on a variety of aspects and features. Let visual clues such as drifts, textured surfaces, and sharp cornices help you identify and avoid steep wind-loaded slopes.

    (4/9/2022)

    Textured surfaces, small developing cornices, and large drifts are all visual clues you can use to help identify wind-loaded areas to avoid.

    Photo: Andy Harrington

  • Storm Slabs

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

    While the strong and shifting winds may headline this event, heavy snowfall rates, fluctuating temperatures, and possibly weak snow surfaces should grab your attention. This combination of factors can easily build strong over weak storm snow. Just because you’re out of the wind doesn’t mean you’re out of danger. Storm slabs will be most reactive during periods of heavy precipitation. While we expect snowfall to taper off after sunrise, if it continues, these slabs could remain quite touchy throughout the day. Any steep open slope should be suspect. Use handpits, uptrack tests, and small slopes to gather information about potential weak layers, including the interface with the most recent storm snow (11/29). Because of the very cold temperatures Tuesday, this could be a particularly weak interface. As you gain elevation these slabs could become larger and more dangerous.

    (11/26/2022)

    Quick hand pits while you travel can give you an indication of how new snow has bonded to old snow surfaces or if it has come in upside down.

    Photo: Andy Harrington

Avalanche Discussion

Steady snowfall and moderate east winds have already begun to impact Snoqualmie Pass. This storm will continue to strengthen overnight Tuesday and should peak in the wee hours of Wednesday morning. With strong winds, fluctuating snowlevels, and high precipitation rates, there could be a small natural avalanche cycle. While we expect that to occur during the night, if you head out for a dawn-patrol, or the heavy precipitation lasts longer than expected, significant avalanche activity could linger further into the morning. 

This is a particularly cold storm for November and may break some of our normal rules of thumb. Don’t be surprised if you see the snowpack act a little differently. An inch of water could turn into 15 inches or more of snow. 

While we expect avalanche activity to involve the new snow above the 11/29 interface, you may still notice other recent storm layers. On Tuesday, prior to this storm, Alpental Patrol reported nearly 2 ft of soft dry snow over the 11/22 rain crust. Even with all the new snow, early-season travel hazards still exist. Don’t let the numerous open creeks, hidden rocks, or thinly buried bushes end your season early.

Regions covered