Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Sep 04 2024 06:28:20 AWUS01 KWNH 040628 FFGMPD TXZ000-041230- Mesoscale Precipitation Discussion 0972 NWS Weather Prediction Center College Park MD 227 AM EDT Wed Sep 04 2024 Areas affected...South Texas... Concerning...Heavy rainfall...Flash flooding possible Valid 040630Z - 041230Z SUMMARY...Highly efficient rain producing, slow moving tropical showers, particularly along the Lower Texas Coast. Localized 2-3"/hr rates may result in localized totals over 5" resulting in rapid inundation flooding. DISCUSSION...Pesky pattern remains across the Northwest Gulf and Deep South Texas again this morning; with core of mid-level shortwave remaining along/just offshore of the Texas coast with some peripheral interaction with base of the elongated northern stream trough that exists across central TX into OK/AR attm. VWP and RAP analysis suggest 850-700mb low remains in the lower Rio Grande Valley just southwest of Starr county in Mexico, which continues to support solid easterly to northeasterly confluent flow across the region advecting the anomalously high and deeply saturated profile with 2.5"+ Total PWats. The boundary layer heating from the western Gulf continues to provide enough thermal support for solid conditionally unstable air with MLCAPE values over 2000-2500 J/kg across S Padre Island, reducing to 1000-1500 J/kg nearer the 850-700mb wave. Recent RAP analysis suggests deep layer moisture convergence is increasing along the 850-700 convergence axis from near LRD to north of PIL. This also is co-located with the col in deep layer steering flow supportive of very slow cell motions for showers that do develop. Given all the factors, flux may be weak but enhanced locally by isallobaric influences of developing convection so rainfall efficiency will by tied to those flux rates, but should be on the order to support 2-3"/hr; perhaps instantaneously higher which could overwhelm any soil condition/limiting infiltration resulting in rapid inundation flooding. Once again, hi-res CAMs are insistent on very high totals where frictional convergence is maximized along the coasts/bays from Corpus Christi southward. 00z HREF values of 3"/6hrs by 12z are even higher than prior days at over 90% while 5" probability is over 50% along much of the coastal length, with 30-50% of 3"/6hrs and 15-25% of 5" as far west as Zapata/Jim Hogg county. While this would normally aspire confidence, these magnitudes have been noted over the last few days and mainly manifested off-shore as propagation vectors were stronger than forecast as inflow/convergence was offshore. Howver, this evening's placement/orientation of the 850-700mb low is observationally further west, perhaps aiding greater convergence onshore and therefore enhancing the potential for flooding conditions. Recent RADAR and 10.3um EIR trends would support this increased coverage and potential. As such, scattered spots of 3-5" and rapid inundation flooding is considered possible, with greater coverage more likely from Corpus Christi Bay southward toward E Cameron county. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7X-PHkczcUSlFQtBF55ols7XHwHVutIvbSquyDQF4j7FJSKCHvzvPJErFmokEqTYSJ1x= _RpUA4nl8Ue7KTRgtZreWb8$ for graphic product... ATTN...WFO...BRO...CRP... ATTN...RFC...WGRFC...NWC... LAT...LON 28449771 28389667 27769701 27079728 26159710=20 25789732 25989821 26359913 26859946 27369963=20 27649965 27909942 28209892 28359831=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) .