Patchy Dense Fog This Morning... Plan on patchy dense fog this morning across the foothills and piedmont of Virginia and North Carolina. This includes the Roanoke Valley and Southside Virginia. The visibility will change rapidly down to one half mile or less in dense fog, especially along area rivers and lakes. Conditions will improve quickly after 8AM. Use caution when traveling this morning. Give yourself extra time to reach your destination. If driving, slow down, use your low- beam headlights, and leave plenty of distance ahead of you.