Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 21 2024 18:32:31 AWUS01 KWNH 211832 FFGMPD SCZ000-FLZ000-GAZ000-ALZ000-MSZ000-220000- Mesoscale Precipitation Discussion 0679 NWS Weather Prediction Center College Park MD 231 PM EDT Sun Jul 21 2024 Areas affected...Central AL...Central & Southern GA...Eastern FL Panhandle...Southwest SC... Concerning...Heavy rainfall...Flash flooding possible Valid 211830Z - 220000Z SUMMARY...Large scale over-turning at peak heating with very deep moisture profile to support efficient rainfall. Deep layer steering may allow for scattered incidents of training/repeating bringing widely scattered spots of 2-4" and possible flash flooding this afternoon into evening. DISCUSSION...A similar weakly forced, deep moisture and unstable environment exists across the Southeast again today. Deep layer positive tilt trough is being reinforced upstream across the Missouri/Mid-Mississippi Valleys, which has left the southern stream in similar orientation with small embedded shortwaves to locally force pockets of thunderstorms. 18z surface analysis shows a surface wave in NE MS connected to a stationary front across much of TN and back into N LA. Deep layer moisture axis extends from the Upper TX coast across S AL/GA; placing the total PWat gradient across central MS, AL into N GA and is reflected in weak pressure trough. Nearing convective temperatures, slight convergence along the trough was sufficient for scattered thunderstorms that have continued to expand/propagate along initial outflow boundaries. Given proximity to 2-2.25" total PWats (over 1" in sfc/850mb layer per CIRA LPW) and deeper warm cloud layer will allow for 2-2.5"/hr rates. Cell motions are slow enough and recent heavier rainfall across central AL/GA has lowered FFG into that range. Howver, training/repeating is likely to be required to reach 3-4" totals for flash flooding to occur in all but urban locations. Profiles and recent visible/RADAR trends suggest some low level moisture is supporting weak outflow boundaries to the south, which may limit that training propagating to the south. Interaction with approaching cells from the Panhandle ahead of a broader meso-high/convective outflow from early morning central may rebuff this propagation and even support mergers across south central GA by 21-22z. A north-south arch of outflow has been converging the highly unstable air across SE AL/SW GA/central FL Panhandle increasing convective coverage, further strengthening the outflow boundary. Deeper southwesterly flow and orientation of cloud streamers off the Eastern Gulf Coast will align for some short-term training as well, so similar to last evening, spots of 2-4" totals may occur inducing flash flooding, though the greatest potential will exist as the two areas merge into the later evening... in a similar axis to last evening's heavy rainfall an saturated ground conditions. Still the magnitude of rainfall is not likely to be very high given cell residency, so overall coverage/incidents of flash flooding are likely to be widely scattered an considered possible these evening.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9cLvrs3YwGMZ3tZ7b4KoI617YpAEkDfuWJiK4sFNyUSGgQ6vjW28uXzAm4GAdW_zzp29= PGu4Vzqd1o2Od-vLJtba91o$ for graphic product... ATTN...WFO...BMX...CAE...CHS...FFC...GSP...JAN...JAX...MOB... TAE... ATTN...RFC...SERFC...NWC... LAT...LON 34338367 34338283 34148146 33768088 33048102=20 32308150 30858294 30138445 30308544 31378575=20 31708625 31738775 31828823 32328842 32778816=20 33298697 33628613 34218424=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .