Don’t light that yule log unless you have a certified woodstove.

Pollution is building up in the Rogue Valley as a ridge of high pressure traps cold air in the valley.

Air quality is moderate this morning, despite Jackson County air quality authorities declaring today a yellow day and restricting burning to only certified woodstoves that emit no visible smoke.

The National Weather Service office in Medford updated an air stagnation advisory this morning.

The advisory warns that air isn’t moving in valley as a layer of cold air is trapped beneath warmer air. Dense, freezing fog that can make roads slippery and increasing air pollution are expected as the inversion strengthens tonight. The stagnant air conditions are expected to linger through Saturday afternoon, the advisory said.

Oregon Department of Environmental Quality warned that stagnant air was expected to linger over much of Southern and Central Oregon. The department asked residents to limit burning as well as driving and vehicle idling.

— Anita Burke