The National Weather Service has issued a winter weather advisory in effect from 4 p.m. today to 4 p.m. Friday.
Lake effect snow is expected to dump 4 to 7 inches of snow across parts of Crawford County during the advisory.
The weather service said a cold front moving through the region will bring scattered rain showers changing over to snow by this afternoon. Winds will shift around to the northwest over Lake Erie, presenting a favorable lake effect snow setup for the higher elevations of northwestern Pennsylvania.
"Snow will become most organized overnight and there may be a brief period of one inch per hour snowfall rates ahead of the Friday morning commute," the advisory said.
The NWS said travel could be very difficult and the greatest snow accumulations are expected in the higher terrain of northern Crawford County and southern Erie County. The service said the main area is expected to be a line from Conneautville to Waterford.