Look for a repeat of the late Wednesday, early Thursday fog tonight through Friday morning.
According to the National Weather Service, the fog will start to drift inland after 8 p.m., but as of Thursday afternoon it is already emerging in some coastal areas.
Visibility is expected to be a quarter or mile or less at times. The weather service warns that driving could be especially hazardous along Interstate 5 Friday morning, and that delays could occur at local airports, including Lindbergh Field and in Carlsbad.
The advisory affects San Diego and Orange counties.
A fog advisory is also in effect for San Diego's valleys, from 11 p.m. Thursday to 9 a.m. Friday.