Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jun 28 2025 00:17:47 AWUS01 KWNH 280017 FFGMPD GAZ000-ALZ000-MSZ000-280430- Mesoscale Precipitation Discussion 0535 NWS Weather Prediction Center College Park MD 817 PM EDT Fri Jun 27 2025 Areas affected...Northwest Georgia, Northern Alabama Concerning...Heavy rainfall...Flash flooding possible Valid 280016Z - 280430Z Summary...Clusters of showers and thunderstorms will continue to drift across Georgia and Alabama through the next several hours. Rainfall rates may pulse up to 2-3"/hr at times during collisions, potentially leading to instances of flash flooding. Discussion...An impressive cluster of thunderstorms has developed over northern GA this evening, while a secondary cluster of slightly less intensity is drifting northward over central AL. These thunderstorms are blossoming despite a weakly forced environment in response to robust thermodynamics characterized by PWs of above 1.75 inches overlapping MLCAPE of 2500 J/kg. Despite modest ascent and negligible shear, leading to pulse type convection, the robust environment is supporting rapid updraft growth on outflow boundaries and during storm mergers, resulting in the clusters currently analyzed on the regional radar mosaic. Radar-estimated rainfall rates have been extreme in northern GA, more than 2.5"/hr, leading to rainfall of more than 2 inches in the past hour at some of the local mesonet stations, and multiple FFW issuances from WFO FFC. The CAMs are struggling to handle the coverage of convection this evening, leading to lower than typical confidence for the next few hours. Although it is likely that convective overturning and a loss of daytime heating/destabilization should result in a gradual downturn of thunderstorm activity (coverage and intensity), the environment for NW GA and northern AL appears favorable for a few more hours of thunderstorms with intense rainfall rates, despite minimal agreement in the CAMs about coverage or placement of convection. Multiple outflow boundaries noted on the national radar composite are all functioning as initiation points for additional cells, and these may merge over northern AL. Where this is progged to occur, MLCAPE is well over 2000 J/kg, and mean 0-6km winds are just 5 kts with chaotic and collapsed Corfidi vectors. This suggests that as storms develop along these boundaries, or due to storm mergers, they will continue to support impressive rainfall rates for which the HREF suggests have a 10-20% chance of exceeding 2"/hr, leading to 15-min rainfall that may reach 0.75" according to the HRRR (3"/hr rates). The slow and chaotic motion of these will cause some places to get repeating rounds or a longer duration of rain, causing as much as 3" of rain in a few areas. 0-40cm soil moisture across much of AL and NW GA is saturated above the 95th percentile, leading to FFG that is as low as 1.5-2"/3hrs, especially over northern AL. The intensity of the anticipated rainfall, combined with the slow motion of developing storms, could exceed these thresholds through around 04Z leading to instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-B7HvunQMIyxYTw1yPmMFjBTsLI2FbLkQcZphIBR-RFhmN_RdIglxW0hZnGnsxHD4KIY= pImIXxKoEYZiK73I7YSIEiQ$ for graphic product... ATTN...WFO...BMX...FFC...HUN...MEG... ATTN...RFC...ALR...ORN...NWC... LAT...LON 34908671 34808519 34558399 34098355 33358340=20 32758353 32538403 32528487 32878597 33288754=20 33528795 34208832 34898810=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) .