Fog has been moving in since the sun set, and visibility is currently a quarter-mile or less, the weather service said.
The advisory in in effect until 6 a.m. Wednesday.
But conditions are expected to improve somewhat after midnight, the weather service said.
Drivers are advised to slow down and leave plenty of distance between cars.
Wednesday's forecast calls for temperatures around 40, winds up to 25 mph and a 40 percent chance of rain or snow.