####018003669#### AWUS01 KWNH 122357 FFGMPD MSZ000-LAZ000-TXZ000-130500- Mesoscale Precipitation Discussion 0261 NWS Weather Prediction Center College Park MD 757 PM EDT Sun May 12 2024 Areas affected...Eastern Texas...Central Louisiana... Concerning...Heavy rainfall...Flash flooding possible Valid 130000Z - 130500Z SUMMARY...Exiting shortwave but increasing diffluence aloft will continue to support a channel of ascent and new development over area of recent rainfall. Training profile would support downstream risk for flash flooding as well as low level flow veers later this evening. DISCUSSION...23z surface analysis denotes a surface wave just west of Houston with a bulge of the warm front across far SE TX before angling southeast offshore of S LA. Aloft, GOES-E WV suite denotes a shortwave crossing northern LA toward the northeast; yet in its wake, the larger scale height-falls over the Southern High Plains are broadening the upper-level flow increasing diffluence aloft for broad scale ascent pattern. As such, VWP and RAP analysis denote the 850mb boundary north of but parallel to the warm front across LA before extending northwest across the Heart of TX toward Northwest TX with some sort of wave near Dallas, that is sliding southeastward. As such, confluent 850mb flow across Southeast TX (southwesterly over the Middle TX coast and southerly east of Galveston Bay) ascends over the boundary and tapping remaining modest instability gradient with MUCAPEs of 1500-2000 J/kg diminishing to less than 500 into northeast TX to central LA. The deep layer convergence is resulting in new development along the axis and southeastward. Deep layer steering has veered a bit to a more westerly component but will allow for training while cells continue to redevelop along the boundary through the late evening/early overnight period. Slowly the 850mb wave will drop south into the Piney Woods and flow LLJ will back further increasing perpendicular ascent for said regeneration. Moisture is not going to be an issue with over 2" total PWATs and downstream 7H RH values over 90% resulting in efficient rainfall production for vertical development along the instability gradient. As such, rats of 1.5"/hr will be common with occasional uptick to 2"/hr with short-term storm scale interactions with other cells, increased convergence. As such, spots of 2-4" remain possible through 06z and given saturated grounds (particularly further west in East Texas), increased runoff is possible to induce localized incidents of flash flooding. Of note: Greatest uncertainty is the possibility of new development closer to the apex of the warm front, in the vicinity of Polk/Trinity/Tyler counties, becoming more surface rooted. This would disrupt the isentropic ascent channel to the north and weaken it, while significantly increasing the potential for much stronger/deeper updrafts and therefore greater rainfall potential (2+"/hr) and would likely quickly induce flash flooding given recent heavy rainfall today and the last week plus. However, will have to watch closely for this evolution though current trends hint less and less from this coming to fruition, but if it does a subsequent MPD will be needed. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...FWD...HGX...JAN...LCH...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 32869597 32829450 32659357 32219201 31859147 31129164 30979253 30489396 30599465 30789531 31649622 32409643 ####018000863#### PENA01 KWNH 121200 @UHPISF000CN MPDSUM@V2.0@0101700060@12120524@@0NMCGPHMPD RP@!' `' ` @ & B7)p&PNAM02@@7~}{{z|}~}}}||}}@@@@@@+l~|{u||@@l@@l@@l0260 @@w0261 @@d&MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d& OF ALL VALID MESOSCALE DISCUSSIONS AT @@d& TIME OF PRODUCT CREATION:@@d& ISSUED 05/12/2024 2357Z @@ dNOAA/NWS/NCEP@@d WEATHER PREDICTION CENTER @@d FOR COLOR VERSION SEE: @@d WWW.WPC.NCEP.NOAA.GOV @