Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Avalanche danger will be rising throughout the day as a potent winter storm impacts the Snoqualmie Pass zone. Avalanches large enough to bury and kill you are expected at upper elevations where the snow is drier. Give the snowpack the time it needs to adjust to the rapid load by avoiding avalanche terrain.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2

    Tuesday is going to be a stormy day at the Pass with moderate to strong winds and plenty of precipitation. We anticipate Storm Slab development at all elevations, but the more dangerous and larger slabs will be found above this past weekend’s rain/snow line. Several rounds of precipitation and fluctuating freezing levels since Friday (2/3 interface) have resulted in several potential failure points capable of producing slides. We are anticipating that there will be natural avalanches big enough to bury or kill you. Tuesday is not the day to hang out in avalanche terrain at mid to upper elevations.

    (2/6/2023)

    An extended column test that failed suddenly and easily on the 2/3 interface on Monday, 2/6. [Draft Dodger Ridge NE 4650']

    Photo: Zack Novak

Avalanche Discussion

The Pass has picked up around 1.5 inches of water since Friday and is expected to double that amount by the end of the day on Tuesday. As was the case over the weekend, the lowest elevations may see rain or a rain/snow mix for much of this event, while upper elevations receive all snow. This will maintain our non-traditional two elevation band forecasting system with one band above this past weekend’s rain/snow line and another below. You can expect to find this transition somewhere in the 4000-4500’ range.

We will be focusing on the snow above the 2/3 interface for this storm, which may be as much as 1-1.5 feet below the surface as of Monday night. High hazard is expected above the rain/snow line where this interface will be continuously loaded throughout the day. On Monday, avalanche professionals in the Alpental Valley found easy propagating test results in large column tests on this layer. 

On slopes that see direct sunshine, the 2/3  likely contains a melt-freeze crust that could make a good sliding surface for avalanches to run on. Observations from the weekend indicate that snow was able to run far distances on this crust in specific locations. On the shadier side of the dial, near-surface facets were observed prior to Friday’s storm and at least one avalanche professional noted snow overlaying these weak grains running far and fast on steeper slopes. Small slabs and mid-storm density breaks were also reported over the weekend by avalanche professionals. 

Below the rain/snow line, the snowpack has seen several rounds of rain and wintery mix since Friday and should be well-suited to handle more. That said, as you ascend in elevation away from the road and closer to the transition point, even areas where the snow was moist could produce some avalanches on steep slopes over 35 degrees. These slides could be either wet or dry depending on the moisture content of the new snow at this elevation. 

We do have some deeper layers of interest between the 2/3 interface and the MLK crust. While we don’t anticipate any of them coming into play tomorrow, some of them could via stepdown by the right avalanche in the right terrain. 

Regions covered