Area Forecast Discussion
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000 FXUS61 KPBZ 210730 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 330 AM EDT Mon May 21 2018 .SYNOPSIS...
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Rain chances return late today through Tuesday as low pressure tracks to our north. The departure of a stubborn front will bring drier weather by Wednesday, with quiet and warm weather expected through Friday under high pressure.
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&& .NEAR TERM /THROUGH TODAY/...
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The ever-present surface boundary currently lying just south of the CWA will get another northward push starting today as a warm front, courtesy of a surface wave along the boundary in the middle Mississippi Valley. The front will not make much northward progress by 00Z, and thus do not make much of a northward PoP push until late in the day. Best chances will lie in southeast Ohio, as well as a secondary maximum in the southeast counties with modest upslope effects. Warm air aloft should prevent much in the way of popup showers and storms initially, until the front lifts into the region. SPC has our southeast Ohio counties in a marginal severe risk for this afternoon and evening. CAMs suggest that the most likely scenario would be initial development in a more favorable air mass over IN/western OH with propagation into the CWA during the evening. A strong to severe wind gust or two would be possible if activity can congeal into multicell clusters/bowing segments. The lack of dry air aloft precludes a downburst risk, and overall wind field is a touch too weak to support persistent, rotating updrafts. Temperatures will run some 5 to 10 degrees above normal today, with much of the southern CWA getting into the lower 80s.
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&& .SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
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The surface low will continue its northeastward push, reaching the southern fringe of the Great Lakes by late tonight, and then western New York by Tuesday evening. Have continued likely PoPs for the Monday night/Tuesday period with a strong moisture punch of 1.5-1.75 inch PWAT values. Also, upper support will be provided from the RRQ of a 250mb jet over southeast Canada and an approaching upper trough. Locally heavy rain will be possible tonight given the high PWAT and relatively slow storm motion, but do not foresee a widespread flooding threat. Depending on how much instability can build up, the arrival of a cold front Tuesday afternoon/evening may present a slightly better risk of severe storms than today for the region as shear could be a bit more pronounced, supporting a gusty wind threat. Most of the area is under a day 2 marginal risk. The aforementioned trough should provide enough of a push to finally move the front away from the region by late Tuesday night or early Wednesday. Have PoPs decreasing from northwest to southeast as a result, ending precipitation by Wednesday evening at the latest. Temperatures will continue to run several degrees above normal through this period.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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High pressure will provide dry weather Wednesday night through Friday at the least. Temperatures will warm slowly as 500 mb heights rise. After the flattening ridge axis passes Friday night, rain chances will increase for the weekend as Great Lakes low pressure approaches. Sunday appears to be the wetter of the two days with the approach of a cold front. Above-normal temperatures will continue.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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Other than patchy early morning MVFR/local IFR fog, VFR conditions are expected for most of today as high pressure slides E across the Ern Great Lakes, though mid/high clouds should increase ahead of an approaching warm front. A few tstms are possible this aftn mainly across OH ports as the front begins to lift N toward the region, and daytime destabilization occurs. Mentioned a VCTS at ZZV. The front should continue its track N tonight with showers and ocnl MVFR conditions overspreading the region. OUTLOOK... Restrictions in showers/tstms are likely Tue/Tue eve with a crossing cold front.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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