Area Forecast Discussion
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000 FXUS61 KPBZ 281741 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 141 PM EDT Sun May 28 2017 .SYNOPSIS... Crossing low pressure will result in areawide showers and thunderstorms this afternoon and tonight. && .NEAR TERM /THROUGH TONIGHT/... Elected to issue a Flash Flood Watch for the southeastern CWA until 02Z, as low-level convergence may combine with terrain to create a few rounds of showers and thunderstorms with heavy rainfall, across an area with lower FFG. Have adjusted PoPs to follow with radar/hi-res model trends. Previous discussion... A small cluster of storms has already formed ahead of the warm front in southeast Ohio. Expecting further formation ahead of the slowly advancing boundary later this morning and this afternoon, with the best focus across northern and eastern sections of the CWA, especially since this region will likely see the best destabilization. Surface-based CAPE values of between 1000 and 2000 J/kg look possible, and with 35-40 knots of shear as well, some scattered severe storms still appear possible. Will also need to monitor rainfall rates, as localized storm training could produce locally heavy totals. The lowest FFG values reside from Allegheny/Westmoreland counties south into northern West Virginia. Cannot rule out isolated high water issues, but not sufficiently concerned to hoist a flash flood watch yet. Will continue to monitor. Shower and thunderstorm chances will continue into tonight as low pressure tracks to our northwest, dragging a cold front across. Coverage will decrease to scattered showers behind the boundary. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... Dry conditions are largely expected on Monday with building high pressure, however, isolated showers cannot be ruled out across northern zones as an upper trough remains over the forecast area and a shortwave brushes by to the north. && .LONG TERM /TUESDAY THROUGH SATURDAY/... The upper trough will remain the dominant feature through the end of the week with no major changes to the longwave pattern. This will result in periodic shower chances as shortwaves propagate within the flow. Temperatures will average near to a few degrees below seasonal levels. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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As of 17Z, isolated MVFR ceilings remain, but should scatter out quickly. Afternoon thunderstorms should develop and remain over eastern portions of the forecast area. While this should generally keep conditions dry at ZZV and probably HLG, all other terminals will have the potential for thunderstorms. Did not have enough confidence in exactly where axis of precipitation will develop to go with prevailing TSRA at this time. As thunderstorms decrease in coverage this evening, a cold front will move in from the west, bringing a round of precipitation to all sites and a shift in wind direction from southerly to westerly. While VFR conditions are expected through the first half of the TAF period outside of any showers/thunderstorms, widespread MVFR/IFR conditions should develop for a few hours behind the front around sunrise. However, by mid morning ceilings should scatter out, yielding a return to VFR conditions. .Outlook... Restrictions are possible Tue/Wed with an upper trough.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...Flash Flood Watch until 10 PM EDT this evening for MDZ001. OH...None. PA...Flash Flood Watch until 10 PM EDT this evening for PAZ021-029- 031-073>076. WV...Flash Flood Watch until 10 PM EDT this evening for WVZ021- 509>514. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.