What causes fog? A meteorologist explains stretch of gloomy Minnesota weather

Days of foggy skies have plagued Minnesota, leading to poor driving conditions and an eerie, film noir-like atmosphere.

The fog is caused by a combination of really warm temperatures in the area and melting snow that brings moisture into the air, said Caleb Grunzke, meteorologist with the National Weather Service’s Chanhassen office.

On top of that, the area is experiencing a stagnant weather pattern without strong upper-level winds that help change the air mass or bring in new air masses from elsewhere, he added.

“This warm, moist air mass has been sitting over us for the last several days, so it just kind of allowed the fog to keep redeveloping and hanging around for this extended period of time,” Grunzke said.

A dense fog advisory, with visibility down to about a quarter-mile, was set to expire at noon Monday. The fog will improve and will be mostly dissipated by tonight, Grunzke said. Beyond that, Minnesota should be fog-free for at least the next several days as the weather turns much colder and drier.

Stagnant air can contribute to poorer atmospheric conditions as air is not circulating from Canada or western parts of the U.S. In the Twin Cities, stagnant air can allow pollution from cars or factories to continually build up in the air, and that can degrade air quality over time. That could affect those with respiratory issues, he said.

While traveling, drivers should use their low-beam headlights and keep plenty of distance from the cars in front of them.