Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 221201 AFDCTP Area Forecast Discussion National Weather Service State College PA 801 AM EDT Thu Jun 22 2017 .SYNOPSIS... A stationary front located just south of the Mason-Dixon line early this morning will lift slowly north across the region today, bringing a return to warmer and much more humid conditions this afternoon right through Friday night. In addition to scattered showers and thunderstorms this afternoon and evening, a plume of deep tropical moisture well to the east of Tropical Storm Cindy, and the remnants of Cindy herself, will stream north into the region for late tonight through friday night bringing more frequent showers and occasional thunderstorms, some of which could produce locally heavy rain of over one inch in just an hour. A cold front will push east across the region during the morning or early afternoon hours Saturday, followed by drier and cooler air with comfortable humidity that will last through much of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Today will begin partly cloudy and comfortable across much of the region with the patchy early fog as a bubble of high pressure slides SE and over us for the late morning. Sfc dewpoints in the 40s across the north, 50s over much of central PA and low 60s in the south will steadily increase during the late morning and afternoon hours. Surface warm front was located just to the south of the Mason-Dixon early this morning, while a well-defined and nearly east/west 925-850mb mean theta-e ridge was located right along the southern border of PA. Regional 88D mosaic loop at 0830Z shows a few showers moving just south of KPBZ and heading toward the Laurel Highlands. Quite an active weather day is possible across southern and western portions of the CWA - especially this afternoon and evening as the warm frontal boundary drifts north and becomes collocated with better deep layer shear beneath a mid/upper level westerly jetlet of 70-80kts. Sfc-1km EHIs climb to between 1.5-2 m2/s2 across the NW mtns between 20Z today and 00Z Friday, with a more compact and slightly weaker area of ML cape and shear lifting north from Scent PA toward the Middle Susq Valley. SPC has the northern mtns of PA in a Marginal Risk for SVR TSRA this afternoon and evening which looks reasonable given the aforementioned features and instability/shear parameters. The front will be followed by a 36-42 hour period of warmer daytime...and much warmer overnight temps and mugginess. Well mixed model soundings and mean 850mb temps around 16C should translate to afternoon max temps from around 80F over the northwest mountains, to the upper 80s across the Lower Susq Valley. Localized heavy showers and thunderstorms today will lay the groundwork/lower FFG values for additional and potentially training convection that will occur Friday, and through Friday night. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... The main focus for convection this evening should be close to the best llvl theta-e convergence and moderate 0-1km shear near the northward advancing warm front that is expected to extend from the NW mtns to the Susquehanna`s West Branch Valley. After 01-02Z, convection should temporarily settle down/lift north into New York State as a weak mid/upper level ridge drifts overhead with a decent mid level cap of around 8-9C blanketing the state. Min temps tonight will be in the mid 60s to l70s with sfc dewpoints tucked in close below - leading to quite a muggy night with variable amounts of clouds at multiple levels, along with patchy late night fog. Friday into Friday night will be the most active weather period of the next 7 days as increasing large scale lift/vertical shear ahead of a potent northern stream trough interacts with the deep tropical moisture and high pwat air in place across the state. SPC has a Marginal Risk painted for all of the state given these factors, and a cold front that will approach the region early Saturday. Basin average rainfall for the 42 hour period late today through early Saturday ranges from around 0.75 of an inch across the east, to between 1.5 and 2.25 inches across the Laurels and points just to the west toward KPBZ. Training Showers and TSRA in this moisture rich environment could quickly increase the Flash Flood potential friday into Friday night, but for now no flags will be issued. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... From a large scale perspective, the medium range forecast will feature a seasonably strong/amplified upper trough settling over the Northeast U.S into next week. Expect moisture/rainfall associated with the remnants of TS Cindy to exit the area by the mid to late morning hours Saturday. Drier, low PW air arrives for the late morning and afternoon hours Saturday and lasts through the weekend. This should translate into comfortable, low- humidity conditions with temperatures near to slightly below late June climatology. Precipitation opportunities will be modulated by several shortwave impulses which have low predictability at this range. Any rains would be generally scattered and on the lighter side given overall lack of deep layer moisture. 21/12z GEFS shows PW values remaining below average into midweek. Temperatures should stay on the cooler side of climo through midweek as the upper level trough shifts east of the area. FWIW the GFS is more bullish vs. EC on heights rebounding/building SE U.S. upper ridging into the second half of next week. That said, there is general agreement in a modest warming trend later next week as the trough moves out and heights return to normal. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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JST and LNS have IFR and MVFR cigs and vsbys respectively. Expect these conditions to improve over the next few hours. A warm front will approach the region this afternoon which should trigger showers and scattered thunderstorms, mainly over the west and NW during the late afternoon with convection continuing into the early evening hours. A better chance for IFR cigs and vsbys will be tonight into tomorrow as warm, humid air overtake the region. .OUTLOOK... Fri...Widespread sub VFR likely with rain and embedded thunderstorms. Sat-Sun...Mainly VFR Mon...Mainly VFR. Chc SHRA/TSRA.
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&& .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... None. && $$ SYNOPSIS...La Corte/Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert/Steinbugl AVIATION...Ceru/Gartner EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.