Air in the Seattle region is expected to get trapped near the surface, including increasingly denser fog and pollutants from cars and chimneys.

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Did you know you can have increasingly heavy fog during an otherwise dry week?

Well, you can. And, in fact, that’s what we are about to experience here in the Seattle metropolitan area, according to the National Weather Service.

Although Monday morning’s fog, which is the result of moisture from the recent rains we’ve had, will likely burn off by midday, that will change as the week goes by, with fog that gets deeper and thicker each day, according to the Weather Service’s Seattle office.

Meteorologist Dustin Guy said a strong ridge of high pressure is likely to bring an extended stretch of rainless days as well as something called temperature inversion.

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“The air actually gets warmer, instead of cooler, as you go up and that traps fog and pollutants and smoke from cars and chimneys near the surface,” he said.

Because the sun is so low in the sky and weak, he said, and because we have no wind or rain to “scour” the air, the fog will have trouble burning off.

“As we get into the second half of the week, the air mass will be increasingly stagnant, and the longer it goes on, the more stuff gets trapped and the more cruddy it gets,” Guy said. “That’s what we’ll be seeing this week.”

Guy said the foggy conditions increase the likelihood of black ice on the roads and urged drivers to use their low beams and give themselves plenty of time to get from Point A to Point B.

Guy said there is no rain in sight for “the foreseeable future,” which means at least until early next week.

“We are looking at a pretty rare event from a climate perspective,” said Guy. “If we get 10 days of dry weather — which is a possibility — it would be the longest stretch of no rainfall in December since 1999,” Guy said. “To find two weeks of completely dry weather, you have to go back to 1985.”

The good news, though, is that if you get tired of the fog, you can always head up into the mountains where the sun will be shining, he said.

“Once you get up over the fog level, it will be very sunny and nice with all the recent snow we’ve had.”

But here in the lowlands, he said,  “the fog will be our main event for a while.”

A dog walker at Magnuson Park on Sunday (Ken Lambert / The Seattle Times)
A dog walker at Magnuson Park on Sunday (Ken Lambert / The Seattle Times)