Synopsis
The basis for the next five days will be the reality of Autumn setting in. Saturday is the autumnal equinox, and the atmosphere will be wasting little time in making us feel the brisk and crisp conditions attributed to the fall season. a weekend washout is in store for the northwestern areas but the southeast will see a distinct contrast this weekend. Beyond this rain system will be the mass ejection of cold air that will kick off autumn with a cooler anomalous start.
Short Term (Now thru Saturday)
The dry air that has given us a nice sunny day today will remain in place to stave off the broken cloud mass off in Ohio. This will keep us cool tonight despite the warm advection setting us up for the weekend activity. The clouds will trudge into the state early Friday morning, and a stationary convergent boundary will align itself from the center of PA through central New England. This convergence amplified by topography will help produce scattered showers Friday afternoon throughout the central third of PA. Following this, a blob of moisture will be ejected out of the ohio valley to join the main system out of Canada. This ejected moisture will ride up the northwest corner of PA, hitting Pittsbirgh and Erie with heavier rain with sporadic downpours earlier Saturday afternoon. Areas in Bradford, Johnstown, and Clearfield (just about 50 miles west of the system) will see just light showers and clouds partially stemming from the boundary to the east. Spots along the eastern half of the state will see showers late Saturday afternoon into the evening, but lighter and more widespread than the stuff out in Erie.
Long Term (Sunday and Monday)
Overnight Saturday into Sunday, the dryslot to this Canadian synoptic system will push all this rain out of the state by Sunday morning, and along with this dryslot lies a heavy isobaric gradient, helping for strong cold advection throughout Sunday, leaving high temps state wide averaging 5 to 8 degrees below average. This transport will remain in effect until high pressure bumps in to weaken the gradient, but the 500mb trough associated with the aforementioned rain will settle in place, keeping a net flow out of Canada and leaving us in a stagnant cold air mass throughout next week. Monday will feature more sun to help with warming, but temps will remain below average for the first half of next week.
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