Area Forecast Discussion
Issued by NWS State College, PA

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760 FXUS61 KCTP 231500 AFDCTP Area Forecast Discussion National Weather Service State College PA 1100 AM EDT Tue May 23 2017 .SYNOPSIS... Rain should pass to the southeast of the area later today and tonight. The most likely period for rain in Central PA will be Wednesday night into Thursday. The weather pattern will be unsettled into the holiday weekend with a few opportunities for rain through Memorial Day. Seasonal temperatures will trend a bit cooler with rain expected late-week, with a modest rebound likely into the weekend. && .NEAR TERM /THROUGH TONIGHT/... Updated the forecast with latest blend and some of the HRRR. Used GOES-16 and HRRR to modify the clouds. There will be cirrus near us all day. But in northern and central areas the cirrus will be thin at times so times clouds and sun. There is some partial clearing in western PA. To the south the clouds are thicker and will thicken as the day goes on. KLWX shows rain mainly south of the DC area at this time. Our blends and the HRRR all want to bring up some light rain to and just across the PA/MD border late this afternoon and evening. Tried to keep POPS in chance range along border a few hours either side of about 8 PM. As the wave moves away overnight any light rain chances slide to our east. Should be areas of patchy fog. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Any fog should burn off in morning Wednesday. Another relatively nice day between QPF events. The approaching lumbering cut-off low is far wetter than the wave that should have missed most of our region on Tuesday. But chance rain should slowly increase late in the day Wednesday in the west and slowly spread east overnight. Most guidance indicates the potential for a 0.5 to 1.0 inch event focused mainly over central PA. The first part of Thursday looks to be quite wet. Previous: The deep closed low evolves slowly east from the Mid MS Valley across the Central Appalachians Wed-Thu with complex surface low occlusion over the OH Valley and secondary development from the Mid Atlantic Piedmont to the New England coast by 26/12z. Despite differences in QPF, the models generally agree with the most likely period of rain from Wed ngt-Thu. Total rain amounts for the 24hr period ending 00z Fri are 0.50-1" and derived from a multi-model/WPC blend. Rain should turn more showery Thu ngt into Friday under cyclonic flow aloft. Temps trend cooler with expected clouds and rain. && .LONG TERM /FRIDAY THROUGH MONDAY/... Cool cyclonic flow on backside of departing cyclone will maintain risk for showers on Friday. A lower-amplitude mid level flow pattern will develop into the weekend with some ridging likely at 500mb. Uncertainty regarding location and timing of shortwave impulses rounding the ridge and effect of prior upstream convection leaves plenty of question marks for Saturday - but there is some agreement in area of max POPs over S OH/into WV and SW PA. NBM/ECE blend yielded the highest POPs for Sunday across Central PA associated with cold front moving south/eastward across the Great Lakes/Appalachians. A severe risk may accompany the cold front but still to early for details. The large scale pattern evolves into a broadly cyclonic regime into early next week around an upper low between the Great Lakes and Hudson Bay. This should keep the pattern unsettled with another round of showers/Tstorms possible next Tuesday. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/...
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Minor adjustments to the TAFS this morning. VFR will dominate today as the only weather issue of note is the high clouds passing across the region. There could be some patchy light rain this evening from KTHV-KCXY-KLNS but it should be very light. Wed morning may feature more fog and low clouds, given that fcst lows are at or below fcst dewpoints, cross over temperatures. Another factor will be that the high clouds could cut down on the cooling late Tuesday and early Wed. Thus for now, just added some fog late. .OUTLOOK... Wed...Evening rain/low cigs possible, esp JST/AOO. Thu...Rain/low cigs likely. Fri...Showers/MVFR cigs NW. VFR SE. Sat...No sig wx expected.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Grumm SHORT TERM...Grumm/Steinbugl LONG TERM...Steinbugl AVIATION...Grumm/Martin

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