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Bye-Bye Sunshine: Marine Push Causes Showers, 20-Degree Drop In Temps

Ed Ronco
A view of Seattle skies in May 2017.

Folks around the Puget Sound region enjoyed a toasty week with temperatures in the 70s starting Tuesday. They even hit the low- to mid-80s in many places in western Washington.  

But the classic northwest “sandals-and-socks” people are now wearing their socks again.

Thursday night, a marine push brought cool onshore flow in from the ocean, pushing temperatures down by about 20 degrees. The cool weather comes with possible showers and is expected to last all weekend long.

“So, the winds were offshore, they turned onshore, temperatures dropped,” says KNKX weather expert Cliff Mass, who is a professor of Atmospheric Sciences at the University of Washington.

“A big, big change,” Mass said. "We went from offshore flow, which brings us warmth and clear skies, to onshore flow, so it just brings that cool marine air in."

Mass says showers in Oregon Friday morning will likely move into western Washington later in the day and continue overnight. The low pressure creating this effect will stick around all weekend.

“Clouds, showers, temperatures only getting up into the mid-50s.” Mass said. “So Saturday’s going to be a radically different day. And Sunday is going to be more of the same.”

Mass says the rain won’t be heavy, just lots of cloudy gray drizzle and showers on and off. Good weather for staying indoors to read a book.

But Mass says he expects the rain to move out  by the middle of next week.

"So, you know it’s going to be kind of a wet weekend," he said.

“Monday, Tuesday will start improving and I think by Wednesday, Thursday, another ridge of high pressure will build in,” Mass said.  “Temperatures will jump back into the lower 70s. So we’re going to see sun again, but it’s not going to be for several days.”

To hear the full conversation, including Cliff’s explanation of what a so-called "marine push" is and how it works... as well as discussion of the torrential rains on Kauai, where nearly 50 inches were recorded in the 24-hour period from April 14-15, you can click on the 'play' icon at the top of this post.

Weather with Cliff Mass airs at 9:02 a.m. Friday, right after BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KNKX environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to podcasts of Weather with Cliff Mass shows, via iTunesor Google Play.

Bellamy Pailthorp covers the environment for KNKX with an emphasis on climate justice, human health and food sovereignty. She enjoys reporting about how we will power our future while maintaining healthy cultures and livable cities. Story tips can be sent to