Area Forecast Discussion
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452 FXUS61 KPBZ 281613 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1213 PM EDT Wed Sep 28 2016 .SYNOPSIS... Upper level low pressure will bring rain to our region for the latter half of the week. && .NEAR TERM /THROUGH TONIGHT/... Early afternoon update featured tweaks to POPs and temperature based on the latest radar, obs, and high res trends. Upper low pressure will continue to dig over the Midwest during the near term. Convective temperature will thus be falling and shower chances increasing today. Dry layers within the atmospheric column will 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 shower chances for the night. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... 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 week. The concern for the period is late Thursday when an Atlantic moisture tap is forecast to stream across areas generally along and north of the PA turnpike, and deepen the overall moisture supply in the column. Currently-progged rain-supporting dynamics are progged for that period, but 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 QPG 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 WEDNESDAY/... 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 /16Z WEDNESDAY THROUGH SUNDAY/... VFR will predominate today, but deterioration can be expected tonight as rain chances increase under the encroaching upper low. .OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/... Periodic restrictions can be expected into the weekend as the upper level low lingers over the region. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ 15 is the U.S. government's official web portal to all federal, state and local government web resources and services.