Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 202253 AFDCTP Area Forecast Discussion National Weather Service State College PA 653 PM EDT Sun Aug 20 2017 .SYNOPSIS... High pressure will bring clear skies and seasonal temperatures to the region tonight. Look for partly cloudy skies with a chance of afternoon thunderstorms on Monday. A strong cold front will approach the region later on Tuesday, bringing a chance of stronger thunderstorms with it. Cooler and drier conditions will return for the second half of the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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Clear skies throughout this evening with strong high pressure and subsidence providing a clear overnight as well. Low temps will be within a degree or two of seasonal norms. Patchy river valley fog expected a few hours either side of sunrise.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... High pressure moves east with southerly and more warm and humid flow returning. Model show a weak shortwave drifting across the area during the afternoon and this combined with heating will trigger a few thunderstorms. Have increased pops to account for this. Any convection will decrease quickly after sunset with a warm and muggy night as area in the warm sector ahead of cold front. && .LONG TERM /TUESDAY THROUGH SUNDAY/... The big weather maker this week still looks to be a potent late summer cold front that will pass through the region Tuesday evening into early Wednesday. After a surge of heat and humidity Monday and Tuesday, with some southern locations possibly nudging 90 each day, the strong front will bring a noticeably cooler and drier airmass to the region starting midweek and lasting through the weekend and into next week. The biggest question will be how much severe potential will accompany the front. Latest timing shows the front just moving through central Ohio by Tuesday evening. The SREF and GEFS develop very limited CAPE near the cold front and into central PA, keeping a finger of unstable air confined mainly to the coastal plain well out ahead of the front. But wind fields increase heading into Tue eve, and this may be enough combined with the difference in the two airmasses to kick storms off and keep them propagating eastward. For now, Slight Risk from SPC encompasses much of the CWA with Marginal Risk in the SE. The remainder of the week into the weekend turns cooler and mainly dry as a sprawling high moves slowly eastward out of southern Canada. Interesting to note that the deterministic models show 850 temps as cold as 3C just north of the Canadian border behind the cold front, a reminder the change in seasons is not all that far away. Chilliest readings look to be the mornings of Fri/Sat/Sun with high centered overhead, dipping lows into the 40s over the Northern Mountains (and deeper valleys of the Central Mountains) and solidly into the 50s elsewhere. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... High pressure over the region will ensure VFR conditions and very light wind for the balance of the evening. Some patchy valley fog is expected across northern Pa early Monday morning, but the odds of significant reductions at any central Pa airfields are low. Perhaps a 10 percent chance of a brief dip to IFR at KIPT around dawn. Scattered afternoon thunderstorms will form Monday afternoon, as high pressure passes east of the region. Despite predominantly VFR conditions, a brief reduction is possible from an afternoon or evening thunderstorm. The best chance will be across the eastern airfields, including KIPT,KMDT and KLNS. .OUTLOOK... Tue...Thunderstorm impacts likely into the overnight. Wed...Morning SHRA...then becoming VFR Thu...VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ross NEAR TERM...DeVoir SHORT TERM...Ross LONG TERM...RXR AVIATION...Ross/Fitzgerald

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