Seattle December dry spell could be longest in 18 years

Late afternoon in Seattle on Wednesday, Dec. 6, 2017, and not a drop of rain in sight. (Photo: KOMO News)

SEATTLE -- It's sunny in Seattle in December, something Seattleites might consider worth celebrating after some of the darkest days in years.

But it's the dryness of the foreseeable future that makes the present weather pattern truly interesting -- historic, you might say.

As it stands, no precipitation is expected for at least the next seven days and possibly longer, a dry spell that would be the longest since 1999, when Dec. 20-29 went without rain.

Possibly, it could be longer than that 10-day spell even.

The blame for this pattern is a ridge of high pressure parked over much of the Western U.S., said Ted Buehner, warning coordination meteorologist for the National Weather Service in Seattle.

And it's not going anywhere.

"It doesn't look like it's going to break any time soon," Buehner said.

The situation creates an inversion layer, with cooler air lower to the ground held down by warmer air up higher. The fog that has been seen around the sound is typical, but a northerly wind has kept it largely at bay, for now.

That wind is expected to shift by next week, which will likely leave the area bathed in fog longer and make for some air stagnation, Buehner said.

Stagnant air and unending fog had a major impact on the region 32 years ago, when Seattle went 14 days without any precipitation in December 1985.

The fog was so heavy and unmoving that flights had to be diverted from Sea-Tac to Portland, recalled Buehner, who was working overnight shifts for the weather service at the time.

"They were running out of room to park the aircraft," Buehner said of the Portland airport.

That year also happened to be the only La Nina year in the 1980s, and Seattle had snow before Thanksgiving.

As the fogs lay in next week, Seattleites may find it an apt time to take a trip west because, as Buehner put it, the coast will be clear.

Winds blowing onshore on the Washington coast will keep the fog down, and that may be the warmest lowland area in the region, he added. is a KOMO News partner. You can read this story at here.

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