Air Stagnation Advisory

The voice on my teevee just told me that the region wherein I reside is under an Air Stagnation Advisory:

Air stagnation is a phenomenon which occurs when an air mass remains over an area for an extended period of time. Due to light winds and lack of precipitation, pollutants cannot be cleared from the air, either gaseous (like ozone) or particulate (like soot or dust). In the United States, the National Weather Service issues an Air Stagnation Advisory when these conditions are likely to occur.

Yep, sounds like the Rogue Valley wintertime.