Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 22 2023 18:21:03 AWUS01 KWNH 221820 FFGMPD SCZ000-FLZ000-GAZ000-ALZ000-222345- Mesoscale Precipitation Discussion 0562 NWS Weather Prediction Center College Park MD 220 PM EDT Thu Jun 22 2023 Areas affected...Southeast Coastal Plain and Piedmont from AL to SC Concerning...Heavy rainfall...Flash flooding possible Valid 221819Z - 222345Z Summary...Showers and thunderstorms developing along a surface front will expand in coverage and train to the northeast through this evening. Rainfall rates of 2-3+"/hr are likely, which in some places could produce more than 3 inches of rain. Flash flooding is possible. Discussion...The GOES-E visible satellite imagery this aftn depicts agitated Cu developing within a warm sector south of a warm front analyzed by WPC across SC. Some enhanced convergent ascent along a cold front dropping out of AL/GA is resulting in some deeper Cu fueling showers and thunderstorms noted on the regional radar mosaic from the Panhandle of FL into parts of southern GA. This front is combining with SPC RAP analyzed SBCAPE of 1500-3000 J/kg and the RRQ of a modest upper jet streak to drive deep layer lift into an environment of PWs measured by GPS of 1.7 - 1.9 inches. Rainfall rates in this fresh convection are already being estimated by KEVX radar to reach 1.5"/hr, and it is likely these rates will continue to intensify through the aftn. As the warm front continues to waver to the north and the cold front sags southeastward, this should result in an environment with even more impressive ascent into increasingly robust dynamics. Southeast flow out of the Gulf of Mexico and the Atlantic will likely wrap even higher PWs northward, potentially eclipsing 2 inches which is above the 90th percentile according to the SPC climatology, with continued high SBCAPE above 2000 J/kg. This will result in increasing coverage of convection as reflected by high-res simulated reflectivity, with intense rain rates of 3+"/hr noted by HREF probabilities producing 15-min rainfall that may reach 1 inch in some areas as progged by the HRRR sub-hourly fields. Motions of these storms will remain quick on 0-6km mean winds of 30 kts to the northeast, but collapsing Corfidi vectors to just 5-10 kts aligned to both the mean flow and the front suggest an enhanced training threat. Where cells train most efficiently, these intense rain rates could produce more than 3 inches of rain. While the intense rates themselves could produce rapid runoff and flash flooding, especially in urban areas, more problematic is that antecedent soils are already primed. 7-day rainfall from AHPS has been generally 300-600% of normal, with 1-3" of rain falling across a lot of this area in the past 24 hours. This has led to regional USGS streamflows that are almost without exception above the 90th percentile. Despite generally high FFG and modest HREF exceedance probabilities, these hydrophobic soils suggest any intense rain will quickly become runoff which could result in instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6s00pvnQ4muVLxCh-4nDsr5rSC41e7_HWgFzzlVTxrO1s38RyavnIm7SGlENRAqSn29r= iKHGFe3MurJKO7ENB7tk8v8$ for graphic product... ATTN...WFO...BMX...CAE...CHS...FFC...GSP...JAX...MOB...TAE... ATTN...RFC...SERFC...NWC... LAT...LON 34388075 34258030 33658015 32828061 32068137=20 31618199 31098292 30738389 30608502 30578616=20 30728669 31178676 31448610 31788509 32488381=20 33188301 33838223 34318159=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) .