Lingering high pressure over the region will allow for lots of sunshine on Monday. An approaching disturbance and associated cold front will move through the state Tuesday into Wednesday, bringing with it scattered showers, possibly moderate to heavy at times. Colder air will build into the state after the passage of the front for the remainder of the week.
Short-Term….
The models all agree that lingering high pressure over the state from the system that will be progressing towards the New England region will keep conditions dry and relatively cloud-free on Monday.
Long-Term….
Some slight uncertainties begin to arise with the timing and extent of precipitation in association with the low pressure system currently developing over the Rocky Mountains region. A well-defined frontal system is projected to form as this low tracks across the US in a northeasterly fashion. The center of the low pressure system itself will pass well to our north north-east later in the week, but the cold front will pass through the state as Wednesday progresses. The 1200 UTC runs of both the WRF and GFS models show the swath of precipitation associated with the cold front entering western regions of Pennsylvania by Tuesday morning. The 900 UTC SREF precipitation ensemble mean shows the main swath of lighter precipitation encroaching upon western Pennsylvania zones by Tuesday morning as well, but has some smaller, spottier bands of showers actually affecting central Pennsylvania hours earlier. We forecasted accordingly. The WRF and the GFS both show more significant bands of precipitation affecting the state beginning Tuesday night, with the heaviest bands passing throughout the day on Wednesday, with the eastern regions experiencing this more towards Wednesday night. The SREF precipitation ensemble mean shows a slightly more organized band of heavier showers charging through the state as Wednesday progresses. We were not afraid to use phrases such as 'rain, heavy at times' for our forecasts, especially on Wednesday. One additional uncertainty was the potential for spotty snow showers mixing in, especially in the more northern or higher elevation regions Tuesday night into Wednesday. This is highly dependent upon how much cold air builds in behind the frontal passage, so we were quite conservative in this respect.
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