...DENSE FOG ADVISORY IN EFFECT UNTIL 2 AM CST SATURDAY... * WHAT...Visibility a quarter mile or less in areas of dense fog. * WHERE...Winnebago, Boone, McHenry, Lake IL, Ogle, Lee, De Kalb and Kane Counties. * WHEN...Until 2 AM CST Saturday. * IMPACTS...Hazardous driving conditions due to low visibility.