Area Forecast Discussion
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000 FXUS61 KPBZ 241048 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 548 AM EST Sat Feb 24 2018 .SYNOPSIS... Periodic rain chances will continue through Sunday. Conditions should be dry for the beginning of the work week, with rain returning to the forecast by Wednesday night. && .NEAR TERM /THROUGH TONIGHT/... Steady light to moderate rain showers are beginning to move into our southern zones, ahead of a shortwave trough poised to move through later today. This wave will ride along a surface frontal boundary that has tried to clear the forecast area, but has thusfar been denied. A surge of warm and moist air through West Virginia will stall the boundary near the Mason-Dixon line through much of the day. As the wave moves west to east over the area, rain showers will spread areawide, but the primary focus of the rain will be south of Pittsburgh. Hi-res models in considerable agreement with the evolution of this wave through the afternoon, and were relied on heavily. Given the surge of PWATs above 1", a strengthening low-level jet, and deep warm cloud layer, rain production should be efficient. These locations will need to be monitored for any localized flooding problems. The wave will pass east this evening, and a another brief lull in rain is expected. PoPs were constructed to be a bit more deterministic with this trend in mind. Showers and the cold front just south of the area will keep our highs a little lower than the last few days, but still above-averages. The aforementioned front will lift north tonight as a warm front. Strong moist and warm advection will fuel moderate to heavy showers lifting north through our forecast area. The axis of this rain will set up north of the axis of today`s rain, giving more spatial dispersion of qpf over the entire area. The result is a slightly lower concern of areal flooding over any one specific area. Still, soils are plenty saturated and an additional 1-1.5" of rain through tonight may be enough to cause some flooding problems. The Areal Flood Watch will continue. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... The period of wet weather comes to an end Sunday as the cold front finally sweeps through the forecast area. This will usher in much drier air that will lead to clearing and increased sunshine through Sunday. Dry weather will carry into Monday and Tuesday as high pressure builds in under nearly zonal flow aloft. The increased sun Monday and Tuesday will keep temperatures above-average. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... Dry weather established early next week will give way to another disturbance near the end of next week. Models continue to show great difficulty in handling the evolution of this next precipitation maker. With much uncertainty, Superblend was utilized heavily in the construction of the extended and, in general, PoPs were kept in the high chance or low likely range. The trend in the forecast that has been a little more consistent is a downward movement in temperatures over next weekend. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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Band of moderate to heavy rain will lift across this morning across mainly northern WV and southwest PA, with IFR ceilings and visibilities in the heavier rain. Otherwise, IFR/low MVFR ceilings will be the rule in more scattered activity. Waves of rain through tonight will keep occasional, hard-to-time IFR restrictions in the forecast, with MVFR ceilings expected outside the heavier rain. Low level wind shear will become a concern overnight as a low level jet continues to transport moisture into the area, maximizing the heavy rain threat. OUTLOOK... Restrictions are expected to continue into Sunday as a cold front passes.
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&& .HYDROLOGY... Numerous forecast points are already at action stages across the region. 2 successive disturbances over the next 36 hours will drop rainfall amounts ranging from 1.00 to 2.00 inches across the region. River Flood watches may need to be converted to Warnings. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...Flood Watch through Sunday evening for MDZ001. OH...Flood Watch through Sunday evening for OHZ039>041-048>050- 057>059-068-069. PA...Flood Watch through Sunday evening for PAZ007>009-013>016- 020>023-029-031-073>076. WV...Flood Watch through Sunday evening for WVZ001>004-012-021- 509>514. && $$

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