Atmospheric conditions likely will cause pollution to accumulate in the Rogue Valley, the National Weather Service warned in an air stagnation advisory issued Friday.
The advisory remains in effect through 4 a.m. Thursday.
High pressure is building over the region, trapping air in the valley, forecasters say. With little movement of air, the amount of airborne particles, including those found in wood smoke and vehicle exhaust, will increase. Air quality is expected to decline.
Meteorologist Sven Nelaimischkies said the weather service coordinates with local air-quality authorities to determine when advisories will be issued.
The Oregon Department of Environmental Quality air-quality monitor in Medford showed the city's air quality was good Friday afternoon, but was rated moderate over a 24-hour period. It had been listed as unsafe for sensitive groups earlier Friday.
The next significant storm that could blow out the stagnant air is expected to arrive late Wednesday or early Thursday.
Find the latest wood-burning advisory information from Jackson County air-quality officials at www.co.jackson.or.us.