Visibility went down as the sun came up Thursday, and the National Weather Service issued a dense-fog advisory through 9 a.m. for all of central North Carolina.
Unusually warm air from the south, laden with moisture, caused the fog that forecasters said would cut visibility to a quarter-mile and sometimes to near zero.
The fog had been lighter before sunrise.
The warm air was expected to bring high temperatures in the 70s later in the day despite cloudiness.
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Forecasters said some fog might even linger all day in western areas of the region.
Friday also was forecast to be ridiculously warm for December, with a chance of the thermometer nearing the record high reading of 80 degrees that was recorded at RDU International Airport in 1998.
After that, however, the cold front that was making life tough in the mountain states Thursday and bringing a range of types of precipitation in the Midwest is expected to reach North Carolina and to bring readings back to reality.
Highs will be in the 40s on Saturday and the 30s on Sunday, and it’s likely to be wet outside