Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Sep 07 2025 18:57:20 AWUS01 KWNH 071857 FFGMPD TXZ000-080100- Mesoscale Precipitation Discussion 1059 NWS Weather Prediction Center College Park MD 256 PM EDT Sun Sep 07 2025 Areas affected...South-Central Texas through the Middle Texas Coast Concerning...Heavy rainfall...Flash flooding possible Valid 071900Z - 080100Z Summary...Showers and thunderstorms will continue to move slowly across the region through the evening. Rainfall rates of 2-3"/hr are likely at times, leading to 2-3" of rainfall with locally higher amounts. This may cause instances of flash flooding. Discussion...The regional radar mosaic this afternoon shows widespread showers with embedded thunderstorms from the southern Hill Country of Texas eastward through the Middle Texas Coast. This activity is blossoming/persisting in response to weak shortwave energy dropping SE around a ridge over northern Mexico, with some of this vorticity likely associated with the remnants of Lorena from several days ago. Additionally, a stationary front is draped across South Texas as analyzed by WPC, which is providing additional focus for ascent through convergence across the area. This lift is occurring within impressive thermodynamics characterized by PWs measured by GPS as high as 2.25 to 2.5 inches, and measured via the KCRP special 18Z U/A sounding of 2.26, approaching the daily record for the date, combined with MUCAPE of 2000-2500 J/kg. This is providing ample fuel for thunderstorm development, and moist-adiabatic lapse rates through 500mb of the area sounding supports the efficient warm-rain processes which have somewhat surprised in intensity so far today in producing MRMS measured hourly rainfall of 1.5 to 2.5 inches, even in modest reflectivity signatures. As the aftn progresses, the CAMs are in good agreement that the focus should become along the stationary front where the enhanced convergence will drive deeper ascent. Modest bulk shear of 20-25 kts will help organize some storms into clusters along this boundary, and as low-level easterly flow intensifies (as reflected by a surge in sfc-850mb LPW), storm motions will collapse to around 5 kts. These slow moving storms will contain rain rates for which the HREF neighborhood probabilities suggest will exceed 2"/hr (as high as a 40% chance), producing locally as much as 0.5" to 0.75" in 15 min as reflected by the recent HRRR. Where storms train or repeat with these rain rates, 2-3" of rainfall with locally higher amounts is expected. Although rainfall south of the Hill Country has been modest recently as reflected by AHPS 7-day rainfall that is generally 10-50% of normal, leading to a sharp gradient and increase in FFG, the region still appears vulnerable to at least isolated flash flood instances through this evening. This is due in part to the efficiency of the anticipated rainfall rates, but also due to expected repeating rounds near the stationary front leading to FFG exceedance as high as 30% from the HREF. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8BuOeNH8btnc9-4e-hEgXHzDm3HK-II08JrsbQzVW3PV4NnEhqWLDBt5_-ws5Xye9dKZ= cGbA6zbBii3y_gbdJF_Rjgs$ for graphic product... ATTN...WFO...BRO...CRP...EWX...HGX... ATTN...RFC...FWR...NWC... LAT...LON 29960018 29919816 29569601 29059580 28469603=20 28149668 27879696 27539711 27289761 27309842=20 27489923 27689976 28100028 29720128=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) .