* WHAT...Visibility one quarter mile or less in dense fog.
* WHERE...Portions of northern, central, and western Iowa. This includes parts of I-35 in northern Iowa, parts of I-80 in western Iowa, and much of US 20 and US 30 in western and central Iowa.
* WHEN...Until 10 AM CDT this morning.
* IMPACTS...Low visibility could make driving conditions hazardous.