We had a wide range in our temperatures this afternoon. The western counties were much warmer than the eastern counties. The eastern counties had an easterly flow of wind. The easterly flow of wind brings cool air from the Atlantic Ocean to Central Pa. This weather phenomenon is called Cold Air Damming.
Cold Air Damming: Cool air is more dense than warm air and so it stays low to the ground. The dense cool air moved into the valleys and became stuck. Cool air has a hard time getting over the mountains. The cool air allows the cloud cover to remain thick and stubborn over the affected areas. This kept our eastern counties high temperatures in the 50s to the 60s.
The western counties had a mix of clouds and sun with a southwest flow. A southwest flow ushers in warm air from the southern states. The combination of a southwest flow and some sunshine made the western counties reach the 70s to the 80s.