Area Forecast Discussion
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000 FXUS61 KPBZ 281838 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 238 PM EDT Wed Sep 28 2016 .SYNOPSIS... Upper level low pressure will bring rain to our region for the rest of the week. && .NEAR TERM /THROUGH TONIGHT/... The late afternoon update featured further tweaks to POPs and clouds based on the latest obs and high res trends which favor a slower precip onset. Otherwise, upper low pressure will continue to dig over the Midwest during the near term. Convective temperature will thus be falling and shower chances increasing through the night. Dry layers within the atmospheric column will continue to provide initial inhibition. Overnight temperature will fall below convective thresholds, but shortwave impulse/occluded front is progged to rotate around the parent-low and maintain likely shower chances for the night. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... The aforementioned low is forecast to briefly stall over the Middle Ohio River Valley on Thursday, before lifting northward and filling once again through the weekend. The concern for the period is for Thursday when an Atlantic moisture tap is forecast to stream across I 68 through Garrett County and over areas generally along and north of the PA turnpike, and deepen the overall moisture supply in the column. Currently-progged rain-supporting dynamics for that period are limited given the lack of convergence/mid level frontogenetical forcing in this mature stage of the low. The better probability for heavy rain off the immediate eastern upslope areas should thus be convection based and instability is not impressive. Have used general River Forecast Center QPF for todays prog of the event in conjunction with WPC QPF probability maps. The bottom line is no flash flood watch until precursor rainfall tonight at least defines a better threat area in conjunction with moisture convergence into the occluded frontal zone. As the Atlantic moisture tap in interrupted by Friday, the sustained rainfall threat will be alleviated with more scattered convection providing the rain chances. && .LONG TERM /SATURDAY THROUGH TUESDAY/... The low is forecast to lift northward and fill through the weekend with dry flow returning and diminishing rain chances for the region, and supporting seasonably warm temperature. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... VFR will predominate into the eveing, but deterioration can be expected tonight and into Thursday as rain becomes likely with moisture streaming into the eastern flank of the upper low. .OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/... Periodic restrictions can be expected into the weekend as the upper level low lingers, then slow lifts north of the region. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ 15/88

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