Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 210909 AFDCTP Area Forecast Discussion National Weather Service State College PA 509 AM EDT Mon May 21 2018 .SYNOPSIS...
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An area of high pressure at the surface will slide by across upstate New York today bringing mostly sunny skies along with comfortable humidity. The frontal boundary that pushes southeast across the region during the late morning and afternoon hours Sunday is now nearly stationary from Central Virginia to the Middle Ohio River Valley. This frontal boundary will lift back quickly to the north as a warm front later today into Tuesday as a weak area of low pressure over the Mid Mississippi Valley races to the Lower Great Lakes Region by daybreak Tuesday. Showers and scattered thunderstorms will spread northeast over the region, becoming concentrated over the Central and Northern counties of the state late tonight through Tuesday morning. A cold front training southwest from the low will sag southeast across the Commonwealth Tuesday afternoon and evening, triggering additional showers and a few strong thunderstorms. a several day period of mainly dry weather with pleasant temperatures is in store for Wednesday through Friday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1025 mb sfc high centered near Alpena Michigan early today will drift to the southeast and supply our region with fair/dry weather, lower humidity and light wind today. Recent rains have left conditions moist, so some early morning fog with vsbys between 1/2SM and 1SM is expected throughout the valleys of northern PA. Temps to start the day today will vary from the low to mid 40s throughout the perennial cold spots across the northern tier counties, to the 60s in the Southern Valleys. A warm front will approach the region from the south late today and tonight with increasing dual to multi layered cloud cover. Latest runs of the HREF and HRRR indicate that any showers won`t develop over/move NE into our Laurel Highlands region until around or shortly afternoon dusk today. 00Z NAM and prior ensembles show PWATs starting to creep up late today and tonight (first across the SW zones). Sfc based cape gets moderately high across far SW PA (1500-2000 j/kg) with llvl based instability in our CWA topping out around 1000 j/kg across far SW Somerset county late today. Due to some disagreement between the dry high res versions, and the coarser regional/synoptic scale models we have a low chc for a few shra/TSRA in the SW late today, while pops are essentially zero elsewhere through at least 06Z Tuesday. Highs today will be rather pleasant topping out in the low to mid 70s across the northern and western mtns, while the valleys of Central and Southern see temps in the upper 70s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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Numerous showers along with a few thunderstorms will bring a several tenths of an inch of rainfall to much of the region tonight into Tuesday before drier air makes a push in from the NW behind a weak cold front starting Wednesday. Tuesday looks like the coolest day of the week, though humidity will be highest. The low temperature tonight will be mainly between 55 and 60, with highs on Tuesday ranging from around 70 degrees across the north, to the mid 70s over much of Central and Southern PA.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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The period from Wednesday through Saturday morning will feature some rare (of late) rain-free conditions, before the chance for a pop-up shower or storm becomes returns for Saturday afternoon. Temps are projected to climb into the 70s each day, with Saturday being the warmest as highs range from the mid 70s to the lower 80s. The coolest morning will be Friday with valleys of the northern mountains dipping into the mid 40s. More active weather returns for late in the weekend as another period of showers and scattered thunderstorms begins, thanks to the persistent north/south plume of tropical moisture that will be nosing back north into the NE US.
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&& .AVIATION /09Z MONDAY THROUGH FRIDAY/... Valley fog will reduce visibility early Monday morning with highest confidence in IFR at KBFD/KIPT. Fog will mix out between 12-14Z giving way to mainly VFR conditions across the airspace through Monday evening. There is about a 50/50 chance for MVFR cigs to develop Monday afternoon over the south central airspace ( invof KAOO) as relatively moist east/southeast flow ascends the higher terrain. High confidence in a period of rain showers w/isolated Tstorm moving across the airspace late tonight into early Tuesday morning 03-12Z. Outlook... Tue...AM rain showers/MVFR-IFR cigs. Sct PM Tstorms. Wed...AM MVFR/IFR cigs wrn 1/3. Thu-Fri...VFR/No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert/RXR AVIATION...Fitzgerald/Steinbugl

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