A moist airmass and surface frontal boundary over southern Iowa later tonight will combine for widespread fog development after midnight. The fog is expected to become thick toward sunrise across the area. Visibility will occasionally reach one quarter mile or less over the advisory area.
Visibility of one quarter mile or less can be expected, especially between 4 and 7 AM early Sunday morning. Travel may be difficult and much slower due to very low visibilities. Allow extra time to reach your destination safely. Follow fog safety rules and use low beam headlights. Check the latest visibility prior to heading out overnight and early Sunday morning.