The National Weather Service has issued a Dense Fog Advisory to be in effect until noon Monday. Visibility in many areas will be less than a quarter of a mile before sunrise. The lowest visibility is expected through 10am. However, areas west of the I-55 corridor will likely see improving visibility by 8am. The fog has been producing a layer of ice and frost due to below freezing temperatures, causing slick spots on untreated roads, bridges and ramps. Driving this morning could be quite hazardous. As a result, so down, use your headlights, and leave plenty of distance ahead of you. Also, be alert for school bus stops which will not be easily seen in advance.