A period of unsettled weather will begin Friday as a weak low pressure system passes through the eastern portion of Pennsylvania, bringing scattered showers to that part of the Commonwealth. This system will be followed by more scattered showers across Pennsylvania as a cold front traverses the region Saturday afternoon into early Sunday morning. Temperatures will plummet behind the passage of the cold front on Sunday, with temperatures not exceeding the upper 40s and low 50s.  Northern and western parts of the Commonwealth look likely to see a freeze on Monday morning. A high pressure system will move into the northeastern United States on Monday, resulting in clearing skies and warming temperatures. Temperatures will continue to climb on Tuesday with most of the Commonwealth exceeding 70 degrees.