Area Forecast Discussion
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000 FXUS61 KPBZ 230334 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1134 PM EDT Tue Aug 22 2017 .SYNOPSIS... Quieter weather Wednesday before showers return Thursday. Cooler and less humid are the themes through the weekend. && .NEAR TERM /THROUGH WEDNESDAY/...
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A cold front is currently slicing through the Pittsburgh area of as of 1130 PM with a line of showers along it that has been fairly persistent. This should hold itself together fairly well as it transits to the southeast given the rather abrupt density discontinuity along the front in the lower levels sa dewpoints drop from the 70s in the 50s over a fairly short distance between Pittsburgh and Sandusky, OH. With the drop in dewpoints in mind, while some fog has developed ahead of the front in the interlude between deeper convection and the shallow activity along the front, once northwesterly dry advection begins in the boundary layer, it would seem additional fog development will become unlikely fairly rapidly. While some 3-5 mile visibilities will be possible through morning, dense fog seems unlikely given isallobaric flow and drier air moving in. With drier air in most of the column for Wednesday, skies should start out most sunny across the board. However, even with a rather dry atmosphere aloft, the mid-level cold pool does transit the southern Great Lakes. This will lead to enhanced lapse rates in the mid-level and some cumulus development. While showers will be most likely generally near and north of Lake Erie, it seems more unlikely that they would spread as far south as I-80. PoPs were kept non-zero, however a mention of showers will not be added to the forecast at this time. Fries
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... Northwest flow aloft allows ripples of energy to round the base of the H5 trough axis positioned over the eastern United States. Plenty of low level moisture in place through Thursday evening to warrant the mention of scattered showers especially for our northern counties closer to Lake Erie. The strongest wave crosses Thursday afternoon, which should bring showers given cooling aloft to the Mason / Dixon line. Future shifts may have to extend the mention of showers to northern West Virginia and western Maryland. Do not expect to see much sunshine Thursday as any heating will fill the sky with a stratocu field. Daytime showers will wane with sunset while anticyclonic vorticity advection. This will start the run of a dry weather the balance of the short term. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Highlights: - Pleasant weather projected - Dry most of the extended - Below normal temps The departing mid level trough and associated low pressure system owes to several nice weather days late this week through the weekend. Surface high pressure builds south from the Great Lakes and with northerly flow on the front end expect below normal temperatures to continue into the middle of next week. Toward the end of the forecast /next tuesday/, moisture from the Gulf resulting from Harvey may provide a canopy of high clouds, but still plenty of time to resolve that over the coming days. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... Drier air and west northwest winds will follow a crossing cold front tonight. There is a low probability of fog development during the predawn hours. .Outlook... No widespread IFR weather is forecast. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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