Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed May 07 2025 06:45:08 AWUS01 KWNH 070644 FFGMPD FLZ000-ALZ000-MSZ000-LAZ000-071300- Mesoscale Precipitation Discussion 0239 NWS Weather Prediction Center College Park MD 243 AM EDT Wed May 07 2025 Areas affected...Central Gulf Coast... Concerning...Heavy rainfall...Flash flooding likely Valid 070700Z - 071300Z SUMMARY...Mature MCS starting to weaken with reduced inflow, but embedded intense rates of 2"/hr will continue to over-run frontal zone and repeat over saturating soils along I-10 maintaining likely rapid inundation flooding concerns through daybreak. DISCUSSION...GOES-E WV suite shows very large, anomalous closed low over the Southern Plains with large mature MCS well displaced at the far eastward extent of its influence. Given the broadening of the larger cyclone, the mid to upper-level forcing is diminishing as the jet slowly reduces in speed and responding winds in the lower levels continue to weaken in turn. While they are weakening, the strength and orientation remain sufficient to maintain the complex throughout the remainder of the overnight period with ideal split in dual jet structure with 100 kt jet lifting northeast across NE TX into TN, while the subtropical jet (60-70kt) ridges ideally, bending southeastward across the western to central Gulf providing excellent divergence/evacuation for to maintain the MCS. The MCS's MCV is over eastern-MS but is slowly shearing along the SW to NE flow and low level winds are veering across the central Gulf, reducing orthogonality of LLJ to the leading squall line across S MS into far SE LA. Source of greatest instability and enhanced moisture also resides upstream into the northwest Gulf, so the fast moving, but intense rain-rates will further reduce overall totals crossing into S AL/W FL though scattered incidents of sub-hourly 1.5-2" remain possible and urban flooding concerns remain. The greater concern remains upstream across western LA into central LA, where outflow from aforementioned bow is starting to lay flat west to east southeast LA, and perhaps align with the slowly sagging cold front. Currently, surface to boundary layer flow remains orthogonal to the boundary-combining front; but 850mb flow is already veering less orthogonal out of the SW to WSW. The jet is also expected to reduce in magnitude from 30kts toward 15kts by 10z, reducing upglide ascent. Given the Gulf remains very warm, MLCAPEs of 2000-3000 J/kg will remain with deep moist profile support 2-2.25" total PWats. So while flux may reduce, the unstable environment will support scattered development from SW LA across south-central LA with capability of 2"/hr rates.=20 Cells will once again cross saturated/flooded areas and maintain ongoing flooding conditions through morning, with slow improvement as scattered cells further reduce to isolated. Still pockets of additional 3-4" totals are probable through 12z and so flooding remains likely especially along of I-10 in LA.=20 Note: Low level flow environment is going to slack for a time toward the end of the valid time; however, there is an upstream shortwave that will trail the right entrance of the exiting upper-level jet streak AoA 12z and appears to be triggering convection west of the Lower Rio Grande Valley currently; this will slide eastward and increase lower level flow/convergence again with another shot of thunderstorms. Will continue to monitor those trends closely. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6aKIpgWB3RtxG-We4i4LuB0Kxg2gwwiQMiQUe5d2tQO0QhHK3OWgvtDBrbc0wkoiDQrx= Uv4OHBbemTT4k2L6O_hSZ2o$ for graphic product... ATTN...WFO...JAN...LCH...LIX...MOB...TAE... ATTN...RFC...LMRFC...SERFC...WGRFC...NWC... LAT...LON 31948811 31928756 31708670 30978638 30348665=20 30038832 29588882 28978910 28938994 28999089=20 29179129 29399197 29629301 29699363 30019361=20 30419304 30899189 31349021 31828881=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) .