Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

An atmospheric river will result in natural avalanche activity at all elevations on Sunday. Many slides will be large enough to bury or kill you. Stay far away from anywhere avalanches can start, run, or stop.

Avalanche problems

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2

    Once precipitation switches to rain, expect natural avalanches to occur on slopes over 35 degrees. You may initially notice loose avalanches as this change occurs. Eventually, more dangerous slab avalanches will fail due to a weak snowpack structure. These slides could travel long distances on open slopes and entrain much of this season’s snowpack. On smooth rock ledges or grassy slopes, the entire snowpack could fail. Traveling in avalanche terrain is not recommended.

    A skier remotely triggered this avalanche in Great Scott Bowl. The crown was roughly 18" deep and 80' wide. [SS-ASr-R1-D1.5-U] Expect similarly sized avalanches on Sunday.

    Photo: Tom C

Avalanche Discussion

Our first winter storm will quickly transition into our first major rain-on-snow event of the season on Sunday. The East flow could result in freezing rain in the morning hours before a complete changeover to rain before noon. Rain should reach most ridgelines as freezing levels rise. Not only will it be very dangerous in the mountains, it will be downright nasty outside.

The Pass has received over 2 feet of snow since Friday. On Saturday, backcountry travelers reported remotely triggering avalanches, shooting cracks, whumpfing collapses, and easy failures in hand pits. This bullseye information reinforces observations of poor snowpack structure and tells us that the snowpack is unhappy. The storm snow sits predominately on a melt-freeze crust at middle to upper elevations, while at lower elevations, it rests on bare ground. This distinction may be important on Sunday. 

We expect larger and more dangerous avalanches in areas where snow existed prior to this storm. This 11/30 interface was the point of failure for multiple avalanches around the region on Saturday, and we anticipate it will continue to be active on Sunday. Avalanches could break even deeper or gouge into older snow layers in isolated areas.

At the lowest elevations, you may find that avalanches are smaller. Any avalanche could be consequential at this time of year due to early-season hazards such as exposed rocks, open creeks, holes, or bushes. 

Regions covered