Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Sep 24 2025 17:40:49 AWUS01 KWNH 241740 FFGMPD MSZ000-LAZ000-TXZ000-242300- Mesoscale Precipitation Discussion 1131 NWS Weather Prediction Center College Park MD 140 PM EDT Wed Sep 24 2025 Areas affected...Middle Texas Coast through southern Mississippi Concerning...Heavy rainfall...Flash flooding possible Valid 241739Z - 242300Z Summary...Showers and thunderstorms will continue to expand across the Central Gulf Coast this aftn. Rainfall rates will likely reach 2-3+"/hr at times, leading to stripes of 2-4" of rainfall. This may cause flash flooding. Discussion...The regional radar mosaic early this aftn shows rapidly expanding coverage of reflectivity associated with increasing showers and thunderstorms from the Middle Texas Coast through southern Mississippi. This activity is blossoming downstream of a cold front that is slowly dropping southeast, driven by an elongated longwave trough axis diving through the Southern Plains. This evolution is driving subsequent downstream jet streak formation, leading to favorable RRQ diffluence aloft. Additionally, spokes of shortwave energy rotating through the trough axis are providing additionally focused ascent. This widespread deep layer lift is impinging into a destabilizing environment reflected by recent SPC RAP analyzed SBCAPE of 2500-3500 J/kg. This instability is combining with impressive moisture (PWs of 2-2.2 inches as measured by GPS) to produce an environment ripe for heavy rainfall production. This is being realized by the expansion of convection, and recent radar-estimated rain rates have peaked above 1.5"/hr, despite current cells featuring relatively small updrafts with short temporal lifespans (pulse variety convection). As the aftn progresses, the high-res guidance is in good agreement that thunderstorm coverage will expand across most of the area, and recent HRRR runs have shown an increasing trend in coverage. This is likely supported by the more favorable overlap of ascent into the rich thermodynamic airmass this aftn, as the trough and accompanying cold front continue to expand southward. Thunderstorms that develop will also be supported by increasing bulk shear to help organize into clusters. This should have the dual-pronged effect of creating heavier rain rates (HREF neighborhood probabilities peak around 40% for 2"/hr coincident with 15-min HRRR rainfall as much as 1", or brief 4"/hr rates) while also leading to longer duration of this rainfall. Additionally, with 850mb inflow remaining out of the Gulf to resupply favorable thermodynamics, propagation vectors collapse to around 5 kts and veer more to the north, indicating that storms will be slower moving and may build south along the TX coast. Where clusters of storms move slowest or backbuild/train, these intense rainfall rates could produce 2-4" of rain (HREF 6-hr rainfall probabilities for 3" above 40%). This will be sufficient to produce rapid runoff even atop the relatively dry antecedent soils. While the greatest threat for impacts will occur where heavy rain falls atop urban areas, any training or repeating of these rain rates across this area could result in instances of flash flooding into this evening. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_zRYIjj0FnOKPOPdWsofhDiO5Tk0fu2rbnBSPvxZt-6moVXQLnEfhWe4TkXBjQZbacQj= VgeYiIcPKq64JIi0A94N8rg$ for graphic product... ATTN...WFO...HGX...JAN...LCH...LIX...SHV... ATTN...RFC...FWR...ORN...NWC... LAT...LON 33139065 33088902 32388871 31468919 30378971=20 30008992 29769040 29679116 29749201 29869315=20 29709382 29489434 29239489 29029541 28909600=20 29089656 29699573 30179528 30739486 31499392=20 32729179=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .