Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You’re most likely to trigger a slab avalanche in wind-loaded terrain on Saturday. Unfortunately, the problem areas may be hidden under a few inches of new snow. So feel for subtle changes in the stiffness of the upper snowpack as you travel to help identify potentially unstable slopes.

Avalanche problems

  • Wind Slabs

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

    Keep an eye out for lingering slabs from Thursday night’s wind event as you ascend in elevation. They may be hidden under a few inches of fluffy snow, so you’ll need to feel for changes in the upper snowpack as you travel to help identify wind-loaded areas. If you encounter stiffer snow, that could feel hollow, you know you’ve found the spots we’re concerned about. Near ridgelines, you still may be able to use visual clues such as newly formed cornices to give you an indication of where some of these slabs may be lurking. Unfortunately, the wind direction has flip-flopped in the last 24 hours meaning you now could find slabs on a variety of aspects. So key into terrain features where they’re more likely such as near ridgelines, on convex rollovers, or rocky terrain such as confined gullies and the base of cliffs.

    (3/10/2023)

    Wind Slabs were hidden under a few inches of new snow but were easy to feel as you traveled terrain on 3/10.

    Photo: Andy Harrington

Avalanche Discussion

On Friday, avalanche professionals and NWAC forecasters around the Pass all reported similar conditions. Newly fallen snow was poorly bonded to a variety of underlying surfaces and was sliding easily due to human triggers. Plenty of recent wind effect, including sensitive Wind Slabs, were observed in wind-prone areas, with the most sensitive pockets found near ridgelines and on convex rollovers. Many of these slabs formed on Thursday night and were hidden under roughly 2-4 inches of new snow.

We should squeeze out a few more inches before Saturday dawns. As a result, don’t be surprised to encounter loose avalanches running on steeper slopes. Most of these should be dry unless the sun is out for a prolonged period of time. It’s that time of the year when anytime the sun comes out and there is new snowfall, you should expect to see Wet Loose activity on steep sun-exposed slopes.

Prior to Thursday’s wind event, the upper snowpack was thought to be generally right-side-up as convective snow showers and periods of sun breaks impacted the zone throughout much of the past week. During this time period, the Pass has received roughly 1-1.5 feet of new snow. You may be able to find some storm instabilities in the upper snowpack such as layers of graupel or fragments of surface hoar, but reported avalanche activity has been limited for a number of days. Earlier this week, some deeper avalanches occurred (D2-2.5) on what is suspected to be the 2/25 interface. It’s been a number of days now and the likelihood is dropping, but if you’re going to encounter an isolated bigger slide it will likely be on this interface, possibly due to a step-down or another large trigger such as a cornice failure.

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