Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Sep 26 2023 17:58:52 AWUS01 KWNH 261758 FFGMPD FLZ000-GAZ000-262355- Mesoscale Precipitation Discussion 1104 NWS Weather Prediction Center College Park MD 158 PM EDT Tue Sep 26 2023 Areas affected...northern FL/southern GA Concerning...Heavy rainfall...Flash flooding possible Valid 261755Z - 262355Z SUMMARY...Efficient thunderstorms will pose a localized threat for flash flooding across portions of northern FL and southern GA through 00Z. Peak rainfall rates of 2-4 in/hr and isolated totals over 5 inches will be possible. DISCUSSION...Radar imagery at 1730Z showed an area of showers/thunderstorms moving east from the Big Bend into north-central FL between 10 and 20 kt, with outflow at its leading edge. These storms have had a history of producing 2-4 in/hr rates and 1 to 1.5 inches of rain in 15 minutes in the vicinity of Apalachicola and the Forgotten Coast earlier this morning. Additional thunderstorms were noted from northeastern FL into southeastern GA with increasing coverage following diurnal heating. The environment was conducive to efficient rainfall production with the 17Z SPC mesoanalysis showing area PWATs of 2.0-2.3 inches, MLCAPE of 500 to 2000+ J/kg and wet bulb zero heights near 14 kft (12Z JAX sounding). There was no shortage of ingredients for lift given the presence of weak surface boundaries and convective induced outflow (surface convergence) along with lift associated with the right-entrance region an upper level speed max over AL/GA into the Mid-Atlantic states. The biggest question for flash flood potential is whether storms will be able to stall long enough over an area to produce high rainfall totals given very high FFG in place across the region. Short term forecasts from the RAP indicate increased 500 mb wind speeds in the vicinity of the FL/GA border between 18-00Z, which will act to increase effective bulk shear values above 30 kt and support more organized, potentially slower moving, cells. It is likely that outflow from the west will merge with ongoing convection closer to the Atlantic Coast and developing storms across inland areas of northern FL. Peak rainfall rates of 2-4 in/hr and localized totals over 5 inches will be possible through 00Z but the higher end of that range will likely remain limited and dry antecedent conditions should limit any flash flooding to urban or other locations with known poor drainage. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8bsAvHW62p5zicyzlWId1pkiHshY8hzA9LxAHBmnvEmiY-StCgfgh3y_Jt6f1tyXyTkw= FKV6f06_EfPgXdN5YCkHL8w$ for graphic product... ATTN...WFO...CHS...JAX...MLB...TAE...TBW... ATTN...RFC...SERFC...NWC... LAT...LON 31548209 31478158 31348116 31098112 30388120=20 29838105 29558093 29018089 28908157 29048195=20 29248245 29518275 29818331 29968354 30308359=20 30678350 31398291=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) .