Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 260327 AFDCTP Area Forecast Discussion National Weather Service State College PA 1127 PM EDT Thu May 25 2017 .SYNOPSIS... Mostly cloudy skies with scattered showers and isolated thunderstorms will persist into the evening hours. A few strong thunderstorms are possible, mainly across south- central and southwestern PA. Scattered showers will linger into Friday followed by a period of mainly dry conditions Friday night into Saturday. Showers and thunderstorms will likely impact the area Sunday into Memorial Day. Today will be the coolest day this week with temperatures rebounding through the holiday weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Fairly persistent convection this evening with persistent weak forcing acting on high deep layer moisture and slow moving weak forcing as double barreled surface low lifts north through the area. Sfc cyclonic flow under cold upper core aloft will continue to support scattered to isolated showers overnight...but earlier heavy rainers have decreased in intensity and heavy rain threat has ended. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... Broad cyclonic/west-northwest flow on southern end of exiting upper trough will support terrain-enhanced showers on Friday before precip winds down Friday night/AM Saturday. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... A lower-amplitude but moderately strong westerly (zonal) mid level flow will set up in the wake of the departing upper trough with modest height rises/weak will ridging aloft into the weekend. A warm front is progged to extend east from surface low in the western Ohio Valley to the mid-Atlantic coast on Saturday. Central PA should reside on the north/east fringe of high instability convective corridor/MCS type pattern expected to evolve from the central and southern Plains to the southern mid- Atlantic coast into Saturday night. The greatest risk for scattered thunderstorms remains over the SW 1/3 of the CWA which is consistent with previous fcsts. SPC has introduced a MRGL risk into this area for D3. The remainder of the area should see a mainly dry start to the holiday weekend but will maintain slight chance POPs. The large scale pattern will evolve into a broadly cyclonic flow regime by Monday with upper trough parked over the Great Lakes and southeast Canada into midweek. The aforementioned warm front will lift north across the area on Sunday followed by a series of weaker cold front associated with shortwave trough rotating around parent upper low centered to the south of Hudson Bay. Ensemble blend still supports max POPs on Sunday/Sunday night into Monday with some additional shower opportunities into midweek as series of shortwaves rotate around mean upper trough. Temps should average pretty close to normal/seasonal to close out the month of May. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Meso anal shows the main surface low just north of PHL as of 11PM. Water vapor loop indicates the axis if the shortwave has shifted to eastern PA with the remainder of the forecast area under the main upper low. Disorganized showers remain, but the overall activity has been diminishing and the near term CAMS show little more than scattered showers floating around for the remainder of the overnight. The bigger picture is starting to show more variable conditions as low level moisture from earlier rains helps in the development of areas of MVFR/IFR. With the upper low continuing to pivot over the state during the evening and overnight, reduced conditions will become more widespread. After some areas of low cigs and fog early in the day Friday, the afternoon will feature mainly VFR with brief MVFR/IFR in scattered showers. Moist WNW upslope flow will continue across the western mountains with the best potential for lingering reduced conditions. .OUTLOOK... Sat...AM fog possible BFD. Sun...Showers/reduced cigs possible, esp Sun night. Mon and Tue...AM low cigs poss west. Sct PM tsra impacts poss east. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Gartner NEAR TERM...DeVoir/Gartner SHORT TERM...Steinbugl LONG TERM...RXR/Steinbugl AVIATION...La Corte

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