Area Forecast Discussion
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000 FXUS61 KPBZ 240133 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 933 PM EDT Sun Jul 23 2017 .SYNOPSIS... A stagnant mid-level trough will keep very humid conditions over the region through Monday with a continued threat for showers and thunderstorms. Dry conditions are expected through early Thursday before a cold front approaches from the northwest. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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A combination of factors is continuing to lead to heavy rainfall over the area this evening. We are implanted directly in the right entrance region of an upper jet streak with a slowly moving short wave trough moving through. This is accentuation differential PVA over the area all while a series of mesolows track out ahead of an incoming cold front in an area of increased low level convergence. Because the pre-frontal activity has been developing in an area of much weaker shear as well as a synoptic scale inflection point, cell movement has been exceedingly slow. This has lead to ample problems with flooding through the evening. While flooding will remain a concern for several more hours, the light is at the end of the tunnel. The regional radar mosaic does indicate the back edge of activity is finally sagging southeastward into central Ohio. While it will take a few more hours to clear our area, it does seem that the heaviest rainfall should be ending shortly. We will continue to monitor flood guidance as many areas are near to critical thresholds. Fog will develop overnight as layer RH values start to fall off, however its ubiquity is questionable until the exact degree of clearing can be ascertained. Fries
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Mid level trough sweeps through Monday afternoon so this will be the last round of showers/storms before a welcome break occurs. Upper level heights will rise on Tuesday, and a broad surface high will build into the Great Lakes. This will finally bring a stretch of dry weather and sunshine for Tues/Wed. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... A deep upper trough and associated surface cold front will settle south from Ontario on Thursday, bringing the threat for showers/storms during the afternoon and evening. Forecast for Friday into the weekend gets a bit muddy. If the aforementioned wave progresses into the Southeast, then the weekend is shaping up to be spectacular with dry conditions and highs around 80. Some model solutions open the upper wave up across the Appalachians keeping the threat for clouds and precipitation (especially over the eastern ridges) into Friday and perhaps Saturday. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Showers and thunderstorms will continue to stream through the area overnight as an upper-level disturbance swings through. This could lead to visibility reduction with heavy rain in the short term. After the showers/thunderstorms move off to the east, deterioration back to MVFR and possibly IFR is expected. A mix of morning stratus and fog is expected over much of the area, with fog favored in the clearing further west. Expecting improvement to VFR through Monday morning. The very slow moving boundary will sag south through Monday, re- invigorating showers and thunderstorms in the afternoon, mainly south of Pittsburgh. .OUTLOOK... VFR is expected to prevail toward midweek as high pressure builds in. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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