Area Forecast Discussion
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454 FXUS61 KPBZ 260116 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 916 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/...
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While the upper level low that has been parked to our south will continue its painfully slow amble to the east, the jet streak to its north should gradually fade through the remainder of the evening. As this occurs, deeper lift in the highly curved right entrance region of this jet will fade from western Pennsylvania. As a result, low level easterly flow around the northern side of this low will have increasing difficulty overcoming the downslope drying from descending from the ridges. As such, light rain will continue to fade into oblivion from south to north generally north of the turnpike over the next couple of hours. On easterly facing ridges, this process will take longer until deeper moisture departs to the east as well. After this occurs, the remainder of the overnight will be dry with decreasing cloudiness. Fries Insolation with rising heights/warm advection in response to a deepening plains trough will resume dry weather for Wednesday, and drive temperature well above the averages. Expect readings either side of the 80 F mark areawide.
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&& .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 /01Z WEDNESDAY THROUGH SUNDAY/... Overall, did not see any reason to make whole-hearted changes from the last TAF issuance. The latest guidance suggests widespread IFR visibility but confidence in this is not high enough for inclusion at all terminals. Still, it appears that skies will begin to scatter out as high pressure builds overhead from the west. Weak southeast wind may be enough to support low MVFR/IFR cigs at the easternmost terminals for much of the night while some fog may develop further west where rain was recorded today. Improvement to VFR is expected after sunrise tomorrow with south-southeast wind remaining under 10kts. .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. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.