Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 23 2024 06:13:35 AWUS01 KWNH 230613 FFGMPD TXZ000-231200- Mesoscale Precipitation Discussion 0704 NWS Weather Prediction Center College Park MD 212 AM EDT Tue Jul 23 2024 Areas affected...Big Bend through east-central Texas Concerning...Heavy rainfall...Flash flooding likely Valid 230612Z - 231200Z Summary...Showers and thunderstorms will expand in coverage along and north of a stationary front overnight. Rainfall rates may reach 3"/hr at times, which through training could produce 2-4" of rain with locally up to 6" in some areas. Flash flooding is likely. Discussion...Reflectivity associated with showers and thunderstorms across portions of Texas tonight has begun to expand in both coverage and intensity on the latest regional radar mosaic. This convection is blossoming across an area with plentiful ascent and in a very favorable environment for heavy rainfall. PWs as measured by GPS are 1.8 to 2.2 inches, and the 00Z U/A sounding out of KDRT measured 2.1 inches. This is collocated with a plume of MUCAPE above 1000 J/kg, aided by an EML noted in the KDRT sounding above 850mb which has likely advected off the Mexican Plateau. Within these impressive thermodynamics, forcing for ascent is increasing as the LLJ has locally backed to the S/SE and increased to 15-20 kts according to area VWPs, which is leading to enhanced isentropic upglide atop a stationary front lying from the Serranias del Burro northeast through the eastern Hill Country. Convergence along the nose of this jet combined with the aforementioned isentropic lift has resulted in an expansion of warm-air advection driven showers, although rain rates have generally remained modest at 0.5-1"/hr so far. The setup is becoming increasingly favorable for training of heavy rainfall leading to flash flooding. As the LLJ continues to intensify to 20-30 kts, it will draw even more robust thermodynamics northward and provide more intense mesoscale ascent. This should result in a rapid expansion of coverage, and many of the CAMs feature widespread activity in the simulated reflectivity, generally along and north of the front. As convection expands, propagation vectors will become increasingly aligned anti-parallel to the mean wind in the vicinity of the front, indicating backbuilding and regenerating cells within this WAA regime. At the same time, mean 850-300mb winds converge into the boundary, suggesting that as cells redevelop they will train repeatedly to the east/northeast. With HREF neighborhood rain rate probabilities reaching 30-40% for 2"/hr, this suggests that locally heavier rain rates of 3"/hr are possible, which through training could produce 2-4" of rain in many areas. Where training is most pronounced, 5-6" of rain is possible as reflected by HREF 5"/6hr probabilities reaching 20-25%, with the best chance according to EAS probabilities being across the southern Hill Country and southern Edwards Plateau. Although there is model uncertainty into the exact evolution and placement of heaviest rainfall, this region is vulnerable to flash flooding. 7-day rainfall according to AHPS has been in some places above 300% of normal leading FFG as low as 0.75-1"/1hr, especially north and east of the Big Bend into the typically vulnerable Hill Country. While that area is most susceptible and features the highest HREF FFG exceedance probabilities, anywhere within the discussion area that receives training of these intense rainfall rates overnight will likely experience instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!82ovdim3VBEt0MtqQPIn5kMf6eI1DxGb8e11CiScrnTRtMzB3UjgNbgacugpRKlNmgJD= 9b6Iz-RphEOjxXVB9xhpThw$ for graphic product... ATTN...WFO...EWX...FWD...HGX...MAF...SJT... ATTN...RFC...WGRFC...NWC... LAT...LON 31349974 31339849 31149732 30719652 30609644=20 29859659 29459716 28899920 28820033 29070131=20 29040134 29470182 29780269 30250251 30900155=20 31210086=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) .