Weather with Cliff Mass
10:40 am
Fri May 2, 2014

Heat Wave Is Over, Another Rainy Weekend In Store

It seems the curse of the wet weekend is upon us again.

This week's unseasonably hot transition from April to May is giving way to much cooler temps and heavy rain on Saturday and Sunday, says KPLU weather expert Cliff Mass.

It comes on the heels of a gloriously sunny and hot work week.

“We’ve had that so many times this year,” said Mass, who teaches atmospheric sciences at the University of Washington. 

Last day of a heat wave is usually the hottest

Mass says the region reached all-time daily records for a number of sites in the Puget Sound area. 

“It was unusually warm, with temperatures getting up to mid-80s, even upper 80s in the interior of western Washington," Mass said.  Seattle hit 85 on Thursday. Mass says that peak came right when he expected it would.

"The last day of the heat wave is often the warmest," Mass said, because the warm periods are most often associated with an area of lower pressure to the South and higher pressure to the north over British Columbia. That brings northerly winds, which are cooler and tend  to push the warm air into our region. 

"But that’s all gonna change now," he  said, because of a  weak front that  is crossing the coast,  bringing clouds and much cooler temperatures with it. Mass says the highs there will only reach into the mid to upper 60s. 

"Here in the interior, the clouds will take a little bit of time to get to us, so I’m expecting temperatures getting into the lower 70s. And some filtered sun, so not a bad day today," Mass said.

"But the rest of the weekend goes downhill fast," as an upper-level low approaches, bringing clouds over most of the area through the whole weekend.

Hold off watering your garden over the weekend

Mass says it will be dry Saturday morning in the lowlands. But rain should be in by lunchtime – probably even earlier than that. And we’ll have moderate rain most of Saturday afternoon and Saturday night.

Sunday morning, there’ll be rain and another system comes in on Sunday. So there’ll be quite a bit of showers, it’ll be heavier in the mountains.

"And so we’re talking about a major shift from temperatures in the mid-80s to Saturday and Sunday it’s going to be only around 60," Mass said.

After that, Mass predicts an improving pattern to start the next work week.

"There’ll be clouds, but much less rain Monday and Tuesday. And then another major system comes in on Thursday. So we’ve switched from having high pressure and a ridge over us, to one where an upper level low is approaching us, right now."

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The weekly KPLU feature "Weather with Cliff Mass" airs every Friday at 9 a.m. immediately following BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KPLU 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 a podcast of “Weather with Cliff Mass” shows.