Synopsis
As the deep upper level trough over the Midwest moves slowly east, it will slowly become separated from the upper level flow and will cutoff. This cutoff low will stall out over the Ohio River valley and leave us in a wet and stormy pattern. An area of low pressure from the south will move into area Friday and promote periods of rain. Once this low exits off to the northeast, the cutoff to the west will provide clouds and a chance of showers through mid-week.
Short Term
Through the morning hours on Friday, the possibility of some clearing tonight will allow for radiational cooling and the formation of fog exists near dawn. However, as shortwave approaches from the south during the day on Friday, there is the strong possibility for moderate rainfall. The 12z European and 12z GFS both are in decent agreement of rain beginning around 18z Friday. Rain will overspread the area and increase in intensity as we approach the evening hours Friday. The rain will become more convective over the eastern portions of PA as we head into Saturday morning. In central to western areas, the rain will gradually subside overnight into Saturday morning. Conversely, in eastern areas, particularly Southeast PA, the rain will continue throughout the day Saturday into Sunday morning.
Long Term
By the midday Sunday, the rain should begin to end in western counties while the rain will gradually subside in eastern areas by Sunday evening. The 21z SREF mean indicates potential total rainfall of 1 to 3 inches of rainfall with closer to 1 inch in western and central areas of the commonwealth. In eastern PA, mainly in extreme southern eastern regions of PA, there could be totals upwards of 3 inches. As the low pressure associated with this shortwave moves off to the northeast, the 500 mb cutoff low will persist to the west and bring more unsettled weather. The cutoff low eventually lifts to northeast mid-week and is replaced by a ridge of high pressure later in the week.
-Matt Mehallow
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