Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240157 AFDCTP Area Forecast Discussion National Weather Service State College PA 957 PM EDT Fri Jun 23 2017 .SYNOPSIS... The combination of an approaching frontal system and the remnants of Tropical Storm Cindy will funnel a plume of deep tropical moisture bringing a steady rain to southern Pennsylvania tonight. Occasional lighter showers are expected across the northwest half of the state through the first half of tonight. The cold front will push east across the region during the morning Saturday, followed by drier and cooler air with comfortable humidity that will last through much of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Showers are becoming more numerous once again as the leading edge of the deep plume of tropical moisture begins to drift across southwestern and south-central PA. Moderate surface and ML instability persists across the Lower Susq Valley this evening, and a few brief, strong TSRA should race quickly ENE across that region within the strongly sheared llvl environment. Temps are still in the mid to upper 70s across the Lower and Middle Susq Valley, while reading across the Central, Northern and Western mtns are in the mid 60s to low 70s. Analysis shows PWATs exceeding 2" (2-4 sigma) in a wide plume from the Louisiana Gulf Coast up into central PA, and moisture transport vectors indicate a continued advection of this tropical airmass into our region. After a few to several more tenths of an inch of rainfall across the Central and Nrn Mtns, with up to an additional 0.50-1.00 inch over the southern tier counties of PA, there could be some minor flooding problems across the Laurels and southern tier counties. However, large scale outflow boundary(s) (seen on satellite animation and regional 88D mosaic) were driving the stronger/heavier rain producing convection to the south of the state tonight. With the steadiest and heaviest tropical rains (and embedded taller convection) impacting the SW counties of the state attm, and the Cfront just making its way inland of Lake Erie`s SE shore, will maintain high pops throughout the first half of tonight. The most vulnerable area for heavy to possibly excessive rain amounts, it looks to be the Laurels where instability will combine with terrain bringing enhanced lift causing localized heavier amounts. As a result we will continue the Flash Flood Watch through 09Z Sat for our SWRN 4 counties. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Conditions will improve rapidly Saturday morning as the deep moisture speeds eastward. NHC expects whatever is left of Cindy to be on the MD coast by 8AM so the best of the rain will be over with drier air sweeping in behind the departing low and cold front. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Models have trended toward much better agreement with the evolution of the seasonably strong large scale upper trough over the Eastern U.S. A couple of shortwave impulses reflecting weak surface fronts or troughs will provide a limited/mainly diurnal opportunity for widely scattered showers/isolated low- topped thunderstorms Sunday-Tuesday. However, much of the this period will be pleasant and dry with below normal PW supporting low humidity and below normal temperatures relative to late June climatology. The trough is fcst to lift out and leave a more zonal pattern by the middle of the week, followed by a resurgence of the Southeast U.S. upper ridge. Models and ensembles show the ridge breaking down in the west as a trough shifts east across the Rockies into the Plains. Southerly flow increasing ahead of its attendant frontal system should result in an upward/warmer trend in temperatures accompanied by low level moisture/humidity. Expect max/min temps to get back to seasonal levels around midweek and likely reaching above normal levels by next Friday. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... Wide range of flying conditions prevail across Central Pennsylvania this evening /00z/. Conditions range from VFR to IFR. This is mainly due to the varying intensity of showers and thunderstorms which continue to sweep across the region. Showers and scattered thunderstorms will persist into the overnight. There will likely be a period of heavier, steadier rainfall between 03z and 09z, with a surge of moisture with the remnants of Cindy, combined with the cold frontal passage. Rain moves off quickly Saturday morning, with a brisk west- northwest wind and a return to VFR conditions. .OUTLOOK... Sat...Scattered restrictions in AM showers...otherwise becoming VFR. Sun...Mainly VFR. Mon-Tue...Mainly VFR, but with a chance of SHRA/TSRA. Wed...VFR. && .EQUIPMENT... KCCX radar will be offline for approximately 4 days starting Saturday, June 24th for technicians to install the first of 4 major service-life extension upgrades. The work on the radar has been scheduled to minimize potential impacts to operations and will be delayed if hazardous weather is forecast. && .CTP WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 5 AM EDT Saturday for PAZ024-025-033- 034. && $$ SYNOPSIS...La Corte/Lambert NEAR TERM...La Corte/Lambert SHORT TERM...La Corte LONG TERM...Steinbugl AVIATION...Jung/Evanego EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.