Weather whiplash: Sunshine won’t last long before rain rolls in Friday

Brace for weather whiplash! There will be plenty of sunshine and warm temperatures Thursday before a big weather change Friday.

The soggy upper-level low that dumped rain across western Washington on Monday is coming back for more. The system rebounds northeast from central California into eastern Washington, taking one more swipe at the region Thursday night and Friday. It will merge with a weak Pacific system tracking southeast from the Gulf of Alaska.

This weather system double-whammy will bring some showers and much cooler temperatures Friday. Thursday’s highs across the interior of western Washington are expected to be well into the 70s, with many of the usual warmer spots like the South Sound toward Portland and the Cascade foothills warming to 80 degrees or better.

But on Friday, high temperatures will plunge close to 20 degrees from Thursday’s warmth, with highs struggling to reach 60. The showers will tend to be scattered, though toward the Cascades, there will be a threat of a thunderstorm Thursday night into Friday morning. A surge in low-level onshore flow from the Pacific will also maintain considerable cloud cover with much cooler air.

Western Washington weekend weather outlook

All is not lost for the weekend. This pair of weather systems is forecast to track inland. In addition, the cooler low-level onshore flow is anticipated to gradually ease. Saturday is expected to have morning clouds with some afternoon clearing, and highs warming into the lower to mid-60s.

By Sunday, any morning clouds are expected to be more short-lived, revealing more sunshine by afternoon. Highs Sunday will continue to rebound, climbing into the mid and upper 60s, even 70 degrees in the usual warmer spots. The average high temperature during the final weekend of May is in the upper 60s.

Early next week, higher pressure aloft is forecast to build over western Washington for more sunshine and continued warming with highs rising into the 70s, just in time for the year’s first 9 p.m. sunset on June 2.

Ted Buehner is the KIRO Newsradio meteorologist. Follow him on X and Bluesky. Read more of his stories here.