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Plenty Of Sun For Seafair, But Lightning Threat Spells Increasing Wildfire Danger

Elaine Thompson
AP Photo
Four of the six members of the Blue Angels, flying U.S. Navy F/A-18 Hornets, billow vapor trails as they arrive at Boeing Field Monday, July 28, 2014, in Seattle.

There will be plenty of sunshine for Seafair weekend, says KPLU weather expert Cliff Mass, but dry conditions and a chance of lightning could mean trouble for firefighters.

Plenty Of Sun In Western Washington

First, the good news: “There’ll be plenty of sun. Don’t worry about that here in western Washington,” Mass said.

The south Sound may see some showers on Friday, but those aren’t expected to stick around this weekend.

Mass predicts temperatures staying pretty warm and “certainly in the 80s” as the weekend progresses, but the mornings will be a bit cooler.

“I wouldn’t be surprised to see some low clouds floating around some areas of western Washington Saturday morning and Sunday,” he said.  

But those clouds will burn off, says Mass, and we’ll have sunny days and temperatures getting up to the low 80s through early next week.

Chance Of Lightning + ‘Explosively Dry’ Conditions = Wildfire Threat

Now, the bad news: A line of thunderstorms and showers is moving up from northern Oregon into southwest Washington and bringing with it the danger of lightning that could spark more wildfires east of the Cascades, says Mass.

“They’re not strong, but there is a line that’s moving northward,” Mass said.

He says the threat of thunderstorms is concentrated over the mountains and in eastern Washington, but the upper-level trough is adding some clouds to the mix west of the mountains as well.  

Mass says the threat of thunderstorms in the mountains will probably get greater on Saturday, especially in the Okanogan.

“We have to keep our eyes on that.” Mass said.

The lightning danger follows the driest week of the year that included above-normal temperatures and a drop in relative humidity. The conditions have made forests and underbrush much like a tinderbox, ready to ignite with even a small spark.

“So it’s warming and drying, the fuels now are explosively dry. Last time we had this situation, lightning came in and ignited more fires,” Mass said.

He says in Wenatchee, the relative humidity dropped below 10 percent on Thursday.

“So I think there’s a really good chance we could see the initiation of more fires,” he said.


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.


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