Area Forecast Discussion
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000 FXUS61 KPBZ 251839 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 239 PM EDT Tue Apr 25 2017 .SYNOPSIS... Building high pressure will return dry, and very warm weather to the Upper Ohio Region for Wednesday. && .NEAR TERM /THROUGH WEDNESDAY/... Upper level low pressure will continue to slowly trundle up the East Coast tonight with increasing subsidence on the western flank suppressing residual rainfall. Boundary layer moisture and a generally warm column should hold morning lows about 7 degrees above the seasonal averages. Insolation with rising heights/warm advection in response to a deepening plains trough will maintain dry weather for Wednesday, and drive temperature well above the averages. Expect readings either side of the 80 F mark areawide. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... Continued warm advection and mixing will support temperatures well into the 80s on Thursday, but the aforementioned plains trough is also progged to dig eastward and increase rain chances as the day progresses. While the low center is forecast to develop toward the James Bay, models have been consistent in extending a negatively tilted axis across the Upper Ohio region in the afternoon or early eve. Should low/mid 80s temperature occur as projected with a near 60 dewpoint, surface based instability would be plenty sufficient to support a severe threat in the progged deep layer shear field. Mid level temperature in association with the fading ridge may provide explosive-inhibition, but current thoughts are the thermal trough may deepen the mid level lapse rates enough to be problematic, especially in light of the developing wind field/high shear environment. An additional point of interest: NAM/GFS indicated mid level veer in association with a negative tilt may support some splitting cells in addition to providing an area of enhanced diffluence at peak heating. At any rate, will begin a Hazardous Weather Outlook mention today with a primary wind threat from short bowing segments supplemented with a large hail threat. Passage of this systems cold/occluding front will end precip during the evening with Friday expected to remain mostly dry and continued warm under a shortwave ridge. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Shortwaves ejecting from a Rockies-to-Plains trough will support periodic rainfall chance for the weekend, timing and placement of which remains questionable given expectations of amplified flow/warm sectorization of the Upper Ohio Region as the Western States system deepens and digs eastward. Very warm temperature will continue until that system shunts a front across the region early next week. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Ceilings will continue to bounce around this evening, with localized MVFR conditions possible from HLG and east. Tonight, remaining cloud cover will lower, but may begin to scatter out as high pressure begins to build from the west. As skies begin to clear west to east tonight, some terminals could see fog development, especially towards daybreak. Easterly winds at 10kts or less will gradually diminish overnight. .Outlook... The next chance for general restrictions is expected with late week low pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ 15

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