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Haze obscures the view of Mount Adams and the Fred G. Redmon Bridge from the Selah Creek Rest Area on Thursday.

Air quality officials are hoping expected light winds this weekend will clear out the smoke-filled Yakima Valley skies.

Yakima and Kittitas counties are under an air advisory until noon Friday, Nov. 8.

Cold, still air at ground level with a warm air mass above has trapped pollutants on the Valley floor, said Mark Edler, administrative division supervisor with the Yakima Clean Air Agency.

For the past week, Yakima County skies have been congested with stagnant air that’s allowed pollutants to build up.

As a result, Clean Air issued a countywide burn ban Nov. 1 that prohibited all outdoor burning and the use of uncertified wood fuel burning heating devices unless they’re the only source of someone’s heat.

The ban was increased Monday to prohibit all fuel burning heating devices — unless it’s the only source of heat — until further notice.

The Yakama Nation initiated a ban of its own on the reservation prohibiting all outdoor burning. Ceremonial burning is exempt.

But relief may be on the way. After experiencing pollutants at unhealthy levels for much of the week, skies countywide improved Thursday to moderate air quality, Edler said.

“Our projection is it may be early next week until we get anything moving through the Valley,” he said. “It’s kind of dependent on getting some air through to move things out.”

Weather forecasters say there’s a chance that light winds this weekend could begin to clear up the skies.

Those winds are expected Friday afternoon and should continue through Saturday, according to the National Weather Service in Pendleton, Ore.

“It should open it up for the rest of the weekend,” said assistant meteorologist Ann Adams.

Patchy freezing fog is expected Friday morning, with temperatures reaching the mid-50s during the day and overnight temperatures dipping to the mid-30s, she said.

Temperatures are expected to rise slightly Saturday and through the rest of the weekend, she said.

An increase in air pollutants sometimes causes a rise in patients at local hospitals suffering respiratory illnesses.

Virginia Mason Memorial Hospital has seen a slight uptick in people complaining of asthma-type symptoms, said hospital spokeswoman Rebecca Teagarden.

This story has been changed to report that Rebecca Teagarden works for Virginia Mason Memorial Hospital.

Reach Phil Ferolito at pferolito@yakimaherald.com or on Twitter: @philipferolito