Fog grounds flights at O'Hare

The National Weather Service has issued a dense fog advisory for the entire Chicago area and a ground stop as been issues for all planes arriving at O'Hare International Airport.

Dense fog has reduced visibility to a quarter mile or less, officials said, causing delayed travel commutes.

In addition, the cold could cause some slick spots on roads due to water freezing on the pavement.

People are urged to slow down and leave plenty of distance between the car in front.