Subj : Heavy Rain/Flood LA/MS/AR To : All From : Mike Powell Date : Mon May 26 2025 09:07:00 AWUS01 KWNH 261401 FFGMPD MSZ000-LAZ000-ARZ000-261900- Mesoscale Precipitation Discussion 0320 NWS Weather Prediction Center College Park MD 1001 AM EDT Mon May 26 2025 Areas affected...Northern LA...Western & Central MS...Southeast AR... Concerning...Heavy rainfall...Flash flooding possible Valid 261400Z - 261900Z SUMMARY...Intense squall line along/ahead of MCV/Cold Pool will track through areas having received heavy rainfall yesterday and again this morning. An additional 1" in 30 minutes followed by shield precip may reaggravate flooding conditions through early afternoon. DISCUSSION...Regional RADAR mosaic depicts a mature MCS with well defined boundary features, with a strong bow/squall line extending from the meso-low southwest of ELD along the state line southwestward into the Piney Woods before becoming oriented west to east across the Heart of TX. An effective warm front has been established along the outflow boundary from yesterday's complex across MS/AL. Solid southerly and southwesterly return flow from the Gulf brings Tds in the the mid-70s and with active scattered convection along it throughout the pre-dawn enhancing a meso-high across E MS; the gradient has sharpened increasing moisture flux convergence along it. Weakening low level flow has reduced convergence but localized clusters, such as the one near HEZ have allowed for focused convection to continue resulting in ongoing flash flooding conditions even prior to the line. As such, portions of southeast AR, Northeast LA and SW MS have seen generally 1-2" with those enhanced hot-spots to 4", reducing capacity of the upper soil column. VWP shows a slow reduction of the LLJ toward 25kts which is veering ahead of the squall line, but the forward speed driven by 1016mb meso-high and northeast shifting MCV into SW AR, convergence will remain strong enough to maintain the northern (southeast propagating) portion of the line. Total moisture over 2" and MUCAPE of 1000-1250 J/kg will allow to maintain solid rainfall production. Rainfall rates up to 1.5"/hr are probable, though only 15-30 minutes of duration will result in a quick ..75-1" in such short duration over the saturated soils that will maintain any ongoing flash flooding or trigger a scattered incident or two along the path generally along I-20. Potential for flash flooding should reduce slightly toward central MS where soils have not been as compromised as locations further southwest, especially near Natchez, MS. It should be noted that additional new stronger development is probable along the downstream edge of the complex into S MS/AL toward afternoon but this is less certain in timing/placement and will watch trends closely for any additional MPD need. Gallina ATTN...WFO...JAN...LCH...LIX...LZK...SHV... ATTN...RFC...FWR...ORN...NWC... LAT...LON 33639133 33229018 32738938 32128904 30988945 30749001 31009111 31189214 31389305 31809355 32499352 33579296 $$ --- SBBSecho 3.20-Linux * Origin: ILink: CCO - capitolcityonline.net (454:3/105) .