...DENSE FOG ADVISORY IN EFFECT UNTIL 10 AM CDT THIS MORNING... The National Weather Service in Des Moines has issued a Dense Fog Advisory, which is in effect until 10 AM CDT this morning. * VISIBILITY...Less than one quarter of a mile. * IMPACTS...Dangerous travel conditions for the morning commute. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Dense Fog Advisory means visibilities will frequently be reduced to less than one quarter mile. If driving, slow down, use your headlights, and leave plenty of distance ahead of you.