Area Forecast Discussion
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000 FXUS61 KPBZ 270059 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 859 PM EDT Thu Apr 26 2018 .SYNOPSIS... Dry weather will continue through midday Friday, with the exception of the Maryland panhandle and adjacent West Virginia mountains as a storm system passes south of the region. Rain chances will return region-wide later Friday and Saturday, as a cold low pressure system slowly meanders through the region. Precipitation amounts will be light. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Late Evening Update... Minor adjustments to the POPs...otherwise no major changes in the forecast. Afternoon Discussion... Seasonably cool, but pleasant day continues across the area, with dry weather expected by and large through the first half of Friday. Mature stacked low centered over NE Mississippi has been a challenge for the NWP model suite over the past few days with respect to storm track, but that has come into excellent agreement with the 12Z runs this morning. The 562dm 500mb height contour appears to be the limiting streamline that will separate this moisture-laden souther stream storm system, from a sharply cooler/drier airmass to its north. Based on this boundary, it appears that any threat of rainfall will be locally confined to the Maryland panhandle and the northeast WV mountains later tonight. Went with a very sharp gradient in both POPs and sky cover across the SE CWA tonight into early Friday, and much of the cloud cover that reaches back toward Pittsburgh should be confined to high cirrus.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/... Southern stream storm system should clear the area after daybreak, leaving a brief period of clearing before the first in a series of northern stream shortwave troughs approached by mid afternoon. It appears that some 3 separate vorticity lobes will pivot across the area between Friday afternoon and Sunday morning, associated with a deep, unseasonably cold mid level low core that will slowly meander through the eastern Great Lakes this weekend. With limited in-situ moisture present, the cold weather impacts will be far more noticed than the precipitation, with vertical support likely sufficient for on/off periods of light rain/drizzle through early Sunday. Did raise the sky cover significantly through the 48-60 hour stretch as deep cyclonic flow, boundary layer instability, and a partial cross-lake fetch will yield in extensive cloud cover through the weekend. Temperatures will run some 15-20 degrees below normal, potentially not breaking 50 in many areas Saturday and/or Sunday. Despite the cloud cover/precipitation, the northern counties and mountain valleys could see low dip slightly below freezing Saturday and Sunday mornings, but we are so far behind on growing degree days that frost headlines aren`t even a remote thought at this juncture. && .LONG TERM /MONDAY THROUGH THURSDAY/... A temporary pattern shift toward much warmer conditions will occur on Monday with the departure of the closed mid-upper low, and a rapid increase in low-mid level heights. Strong warm- advection, especially Monday afternoon should boost highs back to their seasonal average. Continued strong warm advection (850mb temps in the mid teens C) and large scale upper ridging should push temperatures well into the 70s, if not a few 80s on Tuesday, Wednesday and perhaps Thursday. The longevity of the warm air will hinge on the timing of a deep trough that will slowly emerge from a series of severe convective events expected across the southern Plains early next week. Right now have chance POPs as early as late Wednesday, but it could conceivably be Thursday or Friday before that frontal zone reaches the area with the potential for significant rainfall. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... Dry sfc high pressure, under troughing aloft will maintain VFR through Friday morning. The exception will be MGW where MVFR cigs, and possibly some showers will encroach with a shortwave moving across the Central Appalachians early on Friday. Restrictions, primarily MVFR, are then expected to become more widespread toward eve as a cold front slides toward, and then across the region. OUTLOOK... Restriction, primarily MVFR, are likely to persist into early Sunday as cold upper low pressure slides across the area. && .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.