A fog advisory is out for Butler County drivers this morning. Patchy drizzle and rain are expected the rest of the day, according to the National Weather Service.

A dense fog advisory is in effect until 9 a.m. today for Butler County and most of Western Pennsylvania.

The advisory, issued by the National Weather Service in Pittsburgh, notes that the fog is limited to less than one-quarter mile of visibility.

State police advise the heavy fog could make the morning commute tricky, Drivers are urged to slow down, use your headlights, and leave plenty of distance ahead of you.

The weather service forecast is calling for patchy drizzle today before 11 a.m., then rain, mainly after 5 p.m., with a high near 58. Chance of precipitation is 80 percent.

For tonight, expect rain, mainly before 2 a.m. with a low around 30.

Cloudy conditions are to start the day Friday, then gradually becoming mostly sunny, with a temperature falling to around 24 by 5 p.m.