Weekend Pattern Change: Rain, Mountain Snow, and Colder Temperatures

FastCast—Wednesday, Feb. 16 to Wednesday, Feb. 23:

After a few weeks of relatively calm weather, a pattern change is ahead on the weekend. But first, a mostly cloudy reminder of the week is expected, with highs in the upper 40s and lows in the upper 30s to low 40s. Then, a pattern change will take place. The persistent high pressure ridge just off the coast will set up further out to sea, opening the door to weather systems and colder air. Showers on Saturday and Sunday will bring 0.3-0.75 inches of rain to the lowlands, with more on the coast and in the North Sound. The passes will receive snow showers through Monday evening. Expect 8-18 inches of snow at the passes. After the system moves out, colder air will move in. Northerly winds will bring cold temperatures and cold mornings next week. Tuesday and Wednesday mornings in particular will likely have lows in the mid to upper 20s. Details are still evolving, so stay tuned!

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This weekend, the pattern will change from a dominant high pressure ridge just offshore to troughing over the Pacific Northwest. This will allow a weather system and then colder air to move into the area. 

Below is the GFS forecast showing the trough (instead of our constant ridge) over the Pacific Northwest.

This troughing (purple colors over the PNW) will bring a weather system with rain and mountain snow on Saturday and Sunday (with mountain snow showers lingering into Monday).

It’s too early to accurately pinpoint rain and mountain snow totals, but it is safe to expect 0.2-0.75 inches of rain in the lowlands (0.5-1” coast and N. Sound) and 8-18” of snow at the passes through Tuesday.

What is becoming more certain is that there will be colder temperatures on Tuesday and Wednesday mornings of next week. No snow, as there will be mostly clear skies, and potentially biting northerly winds and cold wind chills at times.

The GFS forecast for next Wednesday morning shows cold air around the entire Pacific Northwest.

Zooming in on Washington, and the European model shows quite a cold morning on Wednesday, Feb. 23rd.

While it is too early to know any forecast for certain, be prepared that temperatures could reach as low as the upper teens to low 20s west of the Cascades, and in the teens to the east.

To show that the European model isn’t the lone prediction of cold temperatures, below is the GFS forecast for roughly the same time.

The GFS is a few degrees warmer, but still shows widespread mid to upper 20s west of the Cascades and teens to low 20s to the east.

It is too early to tell many details of the upcoming pattern change, but stay tuned as more details get refined in the coming days!