Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 221054 AFDCTP Area Forecast Discussion National Weather Service State College PA 654 AM EDT Sat Jul 22 2017 .SYNOPSIS... A quasi-stationary frontal boundary will remain in the vicinity of Pennsylvania through Monday. High pressure will build southeast into the region for the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Main focus in the near term is MCS approaching from Ohio. Expect convection to weaken later this morning as it moves into Pa, where CAPEs are much lower. In addition, model soundings indicate low clouds will be slow to mix out over the Laurel Highlands, which will hinder diurnal heating ahead of MCS and reduce the severe threat. Expect a progressively greater threat further east, where model soundings and upstream satellite trends suggest there will be a period of partly sunny skies filtered through some cirrus. The resulting heating/destabilization could allow convection to re-intensify along outflow of remnant MCS over the south central mountains and Lower Susq Valley this afternoon. Latest CAMs, including HRRR/WRF-ARW/NCAR ensemble, all time remnant MCS into the Laurel Highlands around noon, then the Susq Valley by mid afternoon. Model downdraft CAPEs do look favorable for damaging wind gusts across the Lower Susq Valley, if convection re-intensifies. Not much of a severe weather threat over northern Pa today, where very little CAPE is progged north of quasi-stationary boundary. Mainly cloudy skies and showers across the north should cap temps to the upper 70s and low 80s over the northern mountains, while partly sunny skies push readings to near 90F across the Lower Susq Valley. Brightening skies in wake of MCS later this afternoon could set the stage for another round of showers/storms this evening. A quick check of FFG numbers indicates some pockets of wetter ground across central Pa, which could be susceptible to flooding today. NCAR ensemble indicates the possibility of localized amounts in excess of 3 inches possible across the central and south central mountains by this evening. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... A second round of strong to severe convection is possible across the southern half of the forecast area this evening, as strong low level jet and plume of anomalous PWATs works through the area. Bulk of model data then indicates a dwindling chance of showers/storms from north to south overnight. Favorable scenario for additional severe weather across central Pa Sunday afternoon, as the region will be within warm sector south of anomalous surface low tracking eastward along the PA/NY border. Moderate CAPES and moderate westerly flow aloft, combined with large scale forcing ahead of approaching upper trough, should support widespread convection by afternoon. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Some uncertainty continues with regards to timing of upper trough passage early next week, but additional showers/storms appear likely Monday, especially over northern Pa. A period of dry and cooler weather appears very likely by midweek, as upper trough axis finally passes east of Pa and surface high builds into the area. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... IFR cloud deck over far western porton of CWA encompassing DUJ- JST along with some valley fog across the north mountains early this morning, but arrival of cirrus shield will slow expansion of fog heading toward sunrise. Patchy fog restrictions will develop over the lower Susq, though most locales there will remain VFR. After sunrise, fog in the SE half will burn off between 12-13z, and in the NW under the cirrus deck will take into the mid morning to return to VFR. Then attention turns to an approaching warm frontal boundary which will be the catalyst for shower and thunderstorm development around midday in the west spreading eastward in the afternoon. Thunderstorm activity will be most numerous south of I-80 with intermittent restrictions expected into early evening Thunderstorm coverage will diminish but convection will linger over the SE into the overnight. In addition, restrictions will develop over NW half of area. Another round of convection driven by an upper trough will begin to move into western areas around sunrise Sun, which will spread across central PA during the day bringing another period of intermittent restrictions. .OUTLOOK... Sun...AM restrictions likely NW half. TSRA/SHRA likely with intermittent impacts. Sun night...Cig restrictions likely. Scattered TSRA/SHRA. Mon...AM restrictions likely. Scattered TSRA. Tue-Wed...Patchy AM fog. Otherwise no sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald/Gartner AVIATION...RXR is the U.S. government's official web portal to all federal, state and local government web resources and services.