Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jun 25 2023 22:25:20 AWUS01 KWNH 252225 FFGMPD GAZ000-ALZ000-260400- Mesoscale Precipitation Discussion 0580 NWS Weather Prediction Center College Park MD 624 PM EDT Sun Jun 25 2023 Areas affected...eastern AL into western GA Concerning...Heavy rainfall...Flash flooding possible Valid 252222Z - 260400Z Summary...Short term training and merging of cells may produce a quick 2-4 inches of rain along with a localized flash flood across portions of central/eastern AL into western GA. The localized flash flood threat looks to extend through 04Z. Discussion...22Z visible satellite/radar imagery and surface observations placed a convective complex over northern GA along with a southward sagging outflow boundary from southern portions of Middle TN into northern GA. Isolated to scattered thunderstorm activity has been occurring southwest of this complex with a secondary outflow boundary over portions of northeastern AL, with outflow boundary movement toward the south. SPC mesoanalysis data from 22Z showed ample instability ahead of the outflow boundary over AL with 1000 to 3000+ J/kg MLCAPE which lowered to below 1000 J/kg with eastern extent into central GA. Rain-cooled outflow is expected to continue a general movement toward the south over the next few hours with uninhibited instability likely helping to support additional convective development over portions of central AL. Average cell motions should be WNW to ESE or NW to SE, not posing much of a flash flood risk by themselves. However, mean low level flow of 10-20 kt at 850 mb may help to support additional thunderstorm development along the portion of the outflow boundary in AL oriented NW to SE, potentially setting up a situation for repeating and short term training. The potential for repeating, merging and short term training of cells also exists with convection tied to the outflow itself and discrete cells out ahead. Flow aloft is somewhat diffluent which should help to boost upward motion/cell coverage over the next few hours. Rainfall rates near 1 inch in 15 minutes and 2-3 in/hr will be possible with localized totals in the 2-4 inch range through 04Z. While there remains uncertainty regarding convective coverage going through the early overnight hours, an isolated flash flood threat will exist over central/eastern AL into western GA, somewhat conditional on convective coverage. Given fairly high FFG values across the region, the flash flood threat will likely be limited to urban locations and other areas with poor drainage. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_60G44CTFtuWlQQqp3WuaDcDRUSUDn1MFP0ivJApg7xTNndMmCmlDRFmy8vlfKNM_xP_= N4KF93QrZpVXt4-KHgDkc9Y$ for graphic product... ATTN...WFO...BMX...FFC...HUN... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 34408689 33998612 33868500 33398461 32618459=20 32218511 32028598 32158704 32668745 33608752=20 34198737 34388717=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .