The National Weather Service has issued an air stagnation advisory for southwestern Washington, increasing the potential for low air quality in the Vancouver area. Air stagnation is the result of high pressure and light winds. Because there is very little air movement, the potential for pollution is increased and those sensitive to air quality may experience difficulty breathing along with other health problems, the weather service reports. The advisory will last through noon Friday. Wednesday’s forecast shows patchy, freezing fog before 10 a.m. that is expected to gradually clear. High temperatures are expected to be 39 degrees, with temperatures dropping to as low as 27 degrees tonight.