Snow began coming down in some areas before dawn and since then has intensified.
Delaware and Chester counties are getting the worst of it so far. Up to an inch or two is on the ground in places.
State Department of Transportation trucks have been out salting the roads. Some roads are now ice-covered, and dozens of minor accidents have been reported due to the slick road surfaces.
Drivers in Berks and Schuylkill counties reported problems with snow and ice on Thursday evening.
The National Weather Serivce is forecasting mostly lake-effect snow bands across western Pennsylvania on Friday with accumulations generally of 2 to 4 inches. Higher elevations could get more.