Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 282006 AFDCTP Area Forecast Discussion National Weather Service State College PA 406 PM EDT THU JUL 28 2016 .SYNOPSIS... The stalled surface front over the Mason Dixon line will move northward today and tonight as a disturbance approaches from the Ohio and mid Tennessee River Valleys. This will produce a soaking rain over portions of central and south central PA tonight into Friday morning. Behind this system slightly cooler air aloft moves over the region to usher in the weekend. But the ridge may begin to build to our west again early next week. && .NEAR TERM /UNTIL 11 PM THIS EVENING/...
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Flash flood watch issued for southeastern counties. Updated all grids again. Difficulty making gridded temperatures. Nearly all guidance cannot handle the slow rise in temperatures and the depth of the mid clouds blocking the sun. Pretty hard to correctly produce meaningful grids. Better where the HRRR has rain in southwest. But HRRR had really high temperatures today. Not going to happen. Now convection has broken out in the southeast along with the remnant MCS from Ohio now tracking across southwestern Pennsylvania. The more intense convective cores have stayed south of the Mason-Dixon line. But rain in Somerset county and west will move east-northeast across south-central Pennsylvania this afternoon and evening. Expect more showers to develop in southern PA in the warmer air and closer to the boundary. Each HRRR run has different scenarios with evolution and the GFS has the heavy rain axis relatively deep into the cooler air. Cells that develop are slow movers. Lots of uncertainty but from this afternoon on any lumbering convective core has the potential to produce locally heavy rainfall cannot rule out 1-2 inches in 1 hour later this afternoon and into this evening. Our grids show the blended QPF with the 15Z HRRRV1 QPF overlaid for some convective texture. Our QPF is higher in southern/southeastern PA with HRRR based isolated maximum in western Schuylkill county. The GFS still is wetter well north of the CAMS.
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&& .SHORT TERM /11 PM THIS EVENING THROUGH 6 PM FRIDAY/... The rain with embedded heavy showers and storms will continue to over take the region. We kept lowest PoPs and QPF in northwest. Best chance of rain is clearly south and southeast. The GFS rainfall is quite impressive but likely too far north and west based on the CAMS. Things should wind down overnight and early AM. Not as hot Friday and the threat of heavy rain drops off fast in AM and the PoPs will lower as the day goes on. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
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Friday night a short-wave trough will move across Indiana and Ohio spreading showers and possible thunderstorms into western PA. Central PA will see increasing chances for rain becoming likely by afternoon. A second wave moves through in cyclonic flow Sunday keeping the POPs in the 50-70 range with highest chances over the eastern counties. Short-wave moves to the coast Sunday night with ridging building in across Central PA helping clear things out.Monday should be a drier day with sunshine and temps in the 80s.Hi pres ridge should hold through Wednesday though the GFS tries to indicate maybe an isolated afternoon/evening shower or thunderstorm over the Laurel Highlands both days.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/... From KJST across to KLNS showers and rain will affect flying conditions. At each site near and south of this lines showers and thunderstorms will lower visibility and ceilings for the next 8-12 hours. Some of the storms will have intense rainfall. Expect rapid changes to IFR conditions. Large slow moving storms are already present in the flying areas around KTHV-KMDT-KCXY-KLNS. Most of central and southern areas will see periods of rain and thunderstorms this afternoon and evening. MVFR initially to the north but many areas of MVFR to IFR in the south. As the system moves out tomorrow morning conditions should rapidly improve from west to east. OUTLOOK... FRI...Some restrictions in SHRA/TSRA and patchy fog...before 9 AM. SAT- MON...Wide range of conditions expected with a chance of showers and storms. && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Friday morning for PAZ036-056-057-059- 063>066. && $$ SYNOPSIS...DeVoir NEAR TERM...Grumm SHORT TERM...Grumm LONG TERM...Watson AVIATION...Grumm is the U.S. government's official web portal to all federal, state and local government web resources and services.