Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220612 AFDCTP Area Forecast Discussion National Weather Service State College PA 212 AM EDT Sat Jul 22 2017 .SYNOPSIS... Pennsylvania will be on the northern periphery of a subtropical ridge passing across the southern states through the weekend. A few rounds of showers and thunderstorms are expected both Saturday and Sunday, and some could produce gusty winds, hail and heavy downpours. Another cold front will push through the area early next week. && .NEAR TERM /UNTIL 8 AM THIS MORNING/...
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Quasi-stationary front draped across south central Pa early this morning. SPC 05Z mesoanalysis showing around 1000 j/kg of CAPE along this boundary over the Laurel Highlands. Thus, will maintain a slight chance of a shower/storm through dawn across the Laurels and south central mountains. Satellite loop at 05Z is showing some valley fog development across the north mountains, but arrival of cirrus shield will likely limit coverage of fog later tonight. Temps on track to bottom out from the low 60s north of the quasi-stationary front over the northern mountains, to the mid 70s south of the boundary over the Lower Susq Valley.
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Large MCS forms upstream overnight and approaches eastern OH in the pre dawn hours Saturday morning. This feature will be the main player for potential severe weather on Saturday, as strong moisture flux and increasing boundary layer convergence point increase the likelihood of strong to severe storms over PA by late morning and afternoon. CAMs differ on timing and strength of MCS evolution ranging from as early as late morning into my western zones to as late as mid to late afternoon. Think the former is more likely...given quick moisture return late tonight and Saturday ahead of the approaching complex. Severe weather threat will be along and south of warm front, which is progged to reach to near I-80. Not much of a severe weather threat over northern Pa, where very little CAPE progged by latest model data.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... A second round of convection is possible Sat night as strong low level jet and plume of anomalous PWATs works through the area. Convection associated with this feature could potentially evolve into another MCS with potential for overnight severe weather in central PA into Sunday morning. Favorable scenario for additional severe weather across central Pa during the daylight hours Sunday 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. Some uncertainty continues with regards to timing of upper trough passage early next week, but additional showers/storms appear possible. 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 /06Z SATURDAY THROUGH WEDNESDAY/... Quiet night tonight, with most locales remaining VFR, though the usual spiderweb of valley fog will settle into the western and northern mtns. The warm air and high dewpoints will allow for fog formation early, which will mean IFC cigs will form between 04Z to 08Z. Expect them to continue until 12Z to 13Z. Mainly partly sunny skies with increasing clouds through the day with CIGS dropping to MVFR between 18Z to 21Z with showers and thunderstorms in the vicinity of TAF sites after 18Z progressing west to east as a warm front pushes into the region. This will be followed by an upper trough on Sun, which will keep numerous showers and thunderstorms around over the weekend. .OUTLOOK... Sat...AM valley fog possible. TSRA/SHRA likely with intermittent impacts. Sun...AM valley fog likely. Cig restrictions likely north. 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...DeVoir NEAR TERM...Fitzgerald SHORT TERM...DeVoir/Fitzgerald LONG TERM...Fitzgerald/Gartner AVIATION...Ceru is the U.S. government's official web portal to all federal, state and local government web resources and services.