Synopsis: 

A warm front will lift north into Pennsylvania today, bringing along above average temperatures throughout the state.  A cold front from the west will move through Pennsylvania late Thursday afternoon into late Thursday night, before it becomes nearly stationary in the Mid-Atlantic region Friday.  Waves will accompany the stationary front, which is set to bring mix precipitation into the central regions of the state, and light snow accumulations for the western regions of the Commonwealth Friday afternoon into Friday evening.

Short Term:  (Wednesday night through Thursday night)

The fog and the low clouds in the central region have scoured out in the warm sector.  The warm sector has made its way into the area, bringing temperatures 5-10 degrees above normal.  Drizzle and fog will appear tonight due to warm air advection from the south ahead of the cold front.  High temperatures tomorrow could range from 10-20 degrees above normal.  The cold front will arrive into Western Pennsylvania around 18z tomorrow.  Scattered rain showers will arrive ahead of the cold front tomorrow afternoon.

Long Term:  (Friday into the weekend)

An arctic cold front will push eastward toward Pennsylvania Friday night, and bringing artic cold air for Saturday.  This would be the first out of the two mixed precipitation events.  A mild southwest air flow will support rain for most of area Friday, with a changeover to frozen precipitation   from Northwest Pennsylvania to Southeastern Pennsylvania Friday night.  As the frontal boundary moves eastward, colder air will overtake the warm air.  As shortwaves ride northward along the front Friday, air columns will be cold enough to support all snow, which could create accumulations of 3 – 5 inches Friday night.  Another mixed wintry precipitation event will occur on Sunday afternoon.  Medium range models and ensemble guidances depicts a low pressure developoing in the Tennessee valley, and lifting northward during late Saturday into Sunday.  On Sunday, deep moisture and warm air advection aloft over a sub-freezing surface temperature will support frozen precipitation for the area.  GFS and ECMWF guidance shows that freezing rain accumulations could occur early Sunday afternoon into Sunday evening for the central regions of Pennsylvania.  As the models update overtime, the confidence level of the storms track & precipitation type will increase.

~ Chad