Area Forecast Discussion
Issued by NWS State College, PA

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366 FXUS61 KCTP 282033 AFDCTP Area Forecast Discussion National Weather Service State College PA 433 PM EDT Sun May 28 2017 .SYNOPSIS... A warm front over southwestern Pennsylvania late this afternoon will drift slowly northeast across the state tonight and early Monday. A cold front will push east from the Ohio Valley and cross the state during the day Monday. Numerous showers and isolated to scattered thunderstorms will bring locally heavy rain across mainly the southwest third of the state. Low pressure will become stalled over northern Ontario during mid-week and will lead to a slightly cooler than normal and unsettled weather at times during the upcoming week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Widespread overcast deck of stratus and stratocu will remain locked in across practically all of the region through this evening as low-level southeasterly flow ahead of a warm front transports moisture well inland from the Wrn Atlantic. Increasingly strong llvl theta-E convergence within the favorable upslope serly llvl flow regime across the Laurel Highlands and south-central mtns will concentrate the most numerous and heaviest showers and thunderstorms there through dusk. ML cape will also continue to slowly increase along the southern and western perimeter of our CWA late this afternoon and early this evening, within an area of nearly 1.5 inch PWAT air. FFG values are quite low, and the slow moving (and anticipated training/terrain anchored) convection will bring a distinct Flash Flood threat across our SW CWA through early this evening (with a lesser threat across portions of Scent PA that will be deeper into the cool llvl airmass0. Coordinated earlier with KLWX and KPBZ to post a Flash Flood Watch, and that runs until 02Z Monday for Somerset and Bedford counties. Again FFG values are lowest there with the 1-hr amounts needed being in the 1-1.5 inch range, and 3-hour guidance between 1.5 and 2.0 inches. Increasing and moderately strong/veering low to mid-level profile indicates that showers and isolated to scattered TSRA will spread northeast across the entire CWA this evening and overnight. locally moderate to heavy (0.75-1.00 amounts) appear likely, though the steady SW-NE progression of the rain tonight across the Central and NE zones should preclude any appreciable flood threat, other than some ponding and moderate rises on small streams/creeks. The warm front and upper shortwave embedded in the WSW flow aloft will translate to nearly 100 POPs for most of the CWA tonight (though portions of the far SE will see slightly lower POPs after sunset). High temps in the mid 60s to L70s will slide to only the u50s to l60s for overnight lows. Will mention the isold severe threat in the west and SC mtns in the HWO. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... Cold Front will be slicing through Central PA during the mid to late morning hours, crossing the Susq Valley during the early- mid afternoon hours. It should turn out to be a really nice day with just a westerly breeze in the west, but the slowing front may keep it muggier in the east and isold storms would then be possible in the east early in the aftn. Temps may be a bit higher than currently advertised due to some earlier clearing and the downslope effect (especially near the I-99/Route 220 Corridor. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
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The long term period will be dominated by a large upper level low the will slowly moving through the upper Great Lakes and southern Canada. As that quasi stationary low slowly moves to the northeast, it will bring surges of cool moist air across the region. The first surge of cooler air moves across Monday night. This will bring showers in from the W/NW. However, any precipitation will cease as the night continues due to lack of diurnal heating. A reinvigorated boundary should bring a chance of precipitation through the northern half of PA. Several successive shortwave will move through mid to late week which will bring the possibility of scattered showers with preference for the majority of the QPF (albeit quite light at that)to be across the typical west-nwrly flow upslope prone areas of the Laurel highlands and NW mtns. The chance for any thunder will be very minimal Tuesday through Thursday. Generally dry NW flow occurs late in the week into next weekend as a 1020 sfc high over the upper midwest Friday evening builds SE twd the region. Pops Thur night through Fri night will be 30 percent or less. Late in the week the models begin to diverge on the location and timing of the upper level low so there is less confidence on precipitation late in the week. However depending where the boundary sets up there could be periods of showers Friday through Saturday, though currently should be mainly along the Southern border.
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&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/... Early morning fog and very low stratus has lifted to IFR and areas of LIFR cigs across KJST/KAOO and vcnty, while CIGs are mainly a solid MVFR deck across the central mtns of PA (KUNV and KFIG). the best flying conditions this afternoon over northern and eastern PA will slowly deteriorate into the MVFR range late this afternoon and early this evening as a growing area of showers and thunderstorms (along and ahead of a warm front) drift gradually to the NE across the state. The showers (and isolated-sctd mid afternoon to evening training heavier showers and thunderstorms) will lead to localized, greatly reduced cigs and vsbys for brief periods asp across the SW half of the state. More widespread showers, and possible thunder, overnight, with widespread restrictions are expected. A cold front will move through on Monday, ushering out precipitation from west to east during the day. .OUTLOOK... Mon...Showers ending W to E. Restrictions possible. Tue...Scattered showers possible mainly NW. Otherwise no sig wx expected. Wed...Slight chance of showers with reduced ceilings. Thu...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 10 PM EDT this evening for PAZ033-034. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Dangelo LONG TERM...Lambert/Ceru AVIATION...Jung/Lambert

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