The Mat-Su Borough issued an air quality advisory late Thursday for the Matanuska Valley as winds blew through the region.
Officials advised the elderly and people with heart or lung conditions living near Palmer, Wasilla and Butte to stay indoors and limit physical activity, according to an email from the Mat-Su Planning Division. Everyone should avoid "vigorous outdoor activity" until the wind subsides, it said.
Air conditions varied across the Matanuska Valley, according to the Alaska Air Monitoring Network webpage. An air quality index reading at 5 p.m. put Wasilla at 159 and Palmer at 185. Both are "unhealthy for sensitive groups." Butte's air quality index was at 55, which is "moderate."
Bill Ludwig, meteorologist with the National Weather Service, said a high- pressure ridge over central and eastern Alaska is causing the lower air quality and general haze.
The warm air overhead traps the cold air closer to the surface. Cold air doesn't rise into warm air, he said.
"It doesn't let the pollution mix out," Ludwig said. "When they have winds, it tends to stir up the dust."
He expects the high pressure to move out by Saturday.
Call the Air Quality Alert System at 352-3878 for 24-hour updates on air quality in the Matanuska Valley.