Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 230742 AFDCTP Area Forecast Discussion National Weather Service State College PA 342 AM EDT Tue May 23 2017 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Despite a steady stream of high clouds, the visibility has continued to trend lower across parts of the mid-lower Susquehanna Valley with some sites 1/4sm. Will continue to monitor vis trends for possible SPS with impact to the AM commute. Fog should dissipate shortly after daybreak. HIRES model blend keeps the area rain-free through 00z with a consensus "best" chance (15-30%) occurring later this evening across the far southern and southeastern parts of the CWA or mainly to the south of the PA Turnpike. Odds favor the near term period staying dry under thickening high to mid level clouds in advance of deep trough/closed low dropping south from MN to MO by 24/12z.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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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.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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By Friday, the low lifts to our NE as trough axis lifts through. Though the day should bring gradual improvement in the weather, highs Fri could end up several degrees below current guidance in CAA NW flow, a thicker low-level cloud deck and potential for light showers/drizzle - esp NW half of CWA. Sat should bring a return of brighter skies, albeit briefly, and may end up being the nicest day of the long weekend as weak ridge propagates through. Clouds will already be on the increase Sat afternoon and persist into Sun and Mon as a warm front develops over the Ohio Valley (with low pressure gradually organizing over the Midwest). Proximity of this frontal boundary along with deepening trough over the western Great Lakes will bring potential for showers Sun and Mon. Plenty of uncertainty in strength/placement of main weather features across model guidance during this time however, so forecast details remain somewhat elusive for late weekend.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/... 06Z TAFS sent. A slow-moving cold front, located from just east of IPT to around MDT at 03Z, is dying out as it pushes into eastern PA late this evening. West of the front, drier air has arrived and confidence in VFR conditions through tonight is high. East of the front, clearing skies, low dewpoint depressions and light winds will result in areas of fog and low CIGS overnight across eastern PA. Any fog across eastern PA will burn off just after sunrise. Most of the day will feature just some high clouds. Perhaps some light rain late, but mainly south of the TAF sites, based on the airmass in place and guidance keeping most of the area dry. Wed morning may feature more fog and low clouds, given that fcst lows are at or below fcst dewpoints, cross over temperatures. Still time to look this over, as it would be mainly after 06Z. Another factor will be that the high clouds could cut down on the cooling late Tuesday and early Wed. .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. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Steinbugl SHORT TERM...Steinbugl LONG TERM...Lambert/RXR AVIATION...Fitzgerald/Martin

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