Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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715 FXUS61 KPBZ 050203 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1003 PM EDT Thu Jul 4 2024 .SYNOPSIS... A series of disturbances will create periods of scattered thunderstorms through Friday, offering low probabilities for localized flash flooding and gusty wind. Dry weather with seasonable temperature will return Saturday into Sunday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... KEY MESSAGES: - Scattered showers and thunderstorms early this evening will become more numerous - Locally heavy rainfall possible where training occurs ------------------------------------------------------------------- One shortwave/vorticity maximum continues to track across western PA, with a remnant MCV east of PIT. This will exit the region this evening. Another shortwave/vorticity maximum was crossing western Ohio, with additional showers and thunderstorms ahead of it. The next wave should cross the area this evening/overnight, with showers and thunderstorms becoming more numerous. The 00Z PIT sounding shows precipitable water at 2.13 inches, with ML CAPE near 1000 j/kg. Mid level lapse rates are weak with warm air aloft. This is likely the limiting factor on stronger storms this evening. The latest mesoanalysis shows an overall decrease in CAPE values over the last three hours. Shear has increased to near 40kt, though with the weak mid level lapse rates most of the storms have not been able to strengthen. The main concern remains localized flooding where training of thunderstorms occurs. The severe weather potential should gradually wane overnight, with the localized flood potential likely continuing until shortly after midnight. Showers and thunderstorms should taper off from west to east later tonight as the shortwave exits. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... KEY MESSAGES: - More widespread coverage is expected Friday, with damaging wind and flash flood threats remaining possible. - Dry and more seasonable weather returns on Saturday. ------------------------------------------------------------------- A more organized shortwave and surface low pressure crossing the Great Lakes will lift the stationary boundary northward as a warm front and push a late-day cold front through the region. Breaks in cloud coverage and weak cooling aloft should help destabilize the otherwise unchanged environment (modest CAPE, moderate shear, weak lapse rates, high PWAT values). The expectation is for greater shower and thunderstorm coverage during the afternoon and evening Friday ahead of each boundary, with damaging wind and localized flash flooding threats possible. Improved forcing and instability should be negated by stronger storm flow to leave the overall flash flood threat similar to that seen today. Passage of the surface cold front and upper shortwave will diminish storm chances Friday night, with dry and seasonable weather returning on Saturday. && .LONG TERM /SUNDAY THROUGH THURSDAY/... KEY MESSAGES: - High probability for dry weather and slightly above average temperature the rest of the weekend. - Unsettled weather returns Tuesday through at least mid-week. ------------------------------------------------------------------- Confidence remains high in dry weather continuing through the weekend as surface ridging remains over the Ohio Valley and upper troughing persists over the Central Plains. Temperatures should remain near-normal on Sunday, but increasing return flow and warm advection on Monday ahead of the next low pressure system will drive daily highs back above-normal. Ensembles indicate more active weather Tuesday into mid-week as low pressure crosses and upper troughing sets up across the East. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Hi-Res guidance has been consistent that cigs will drop to MVFR/IFR into early tomorrow morning as a new mesoscale feature advances into eastern Ohio and western PA and stirs a new round of convection. Isolated showers/storms that advance over terminals may experience a brief period of IFR/LIFR vis. However, with convection being so disorganized, confidence is low on which terminals will be impacted in advance; amendments will likely be necessary while monitoring the radar. IFR to MVFR conditions may linger through 16Z under a lingering warm, moist air mass. Additional rounds of showers and thunderstorms (with occasional restrictions) are expected through early Sat as a cold front slowly crosses. Any storms in the vicinity of terminals could drop restrictions to MVFR/IFR briefly, especially vis with heavy downpours. .Outlook... VFR should return Sun amid high pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Frazier NEAR TERM...WM SHORT TERM...Frazier LONG TERM...Frazier AVIATION...Hefferan