Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Apr 21 2025 21:09:45 AWUS01 KWNH 212109 FFGMPD MSZ000-LAZ000-220110- Mesoscale Precipitation Discussion 0155 NWS Weather Prediction Center College Park MD 508 PM EDT Mon Apr 21 2025 Areas affected...southern MS into southeastern LA Concerning...Heavy rainfall...Flash flooding possible Valid 212107Z - 220110Z Summary...Training/backbuilding cells will continue a flash flood threat for portions of southeastern LA into southern MS through 01Z. Localized high rainfall rates in excess of 3 in/hr will be possible. Discussion...Visible satellite and regional radar imagery at 2045Z showed scattered thunderstorms extending from south-central MS into southeastern LA, with low level moisture feeding an unstable (1000-2000 J/kg MLCAPE) and moist (1.5 to 1.7 inch PWATs) airmass into the region via southerly 10-15 kt 925-850 mb winds. Given similarly oriented and slightly weaker deeper layer steering flow, elements of training and backbuilding have been observed near downtown New Orleans and the I-10 corridor to the west. Several reports of rainfall rates exceeding 1 inch in 15 minutes and 3 inches per hour have been observed in this area of LA. Aloft, initiation was augmented by lift ahead of a subtle shortwave aloft over the western Gulf and an upper level jet max crossing northern Mexico and southern TX, with divergence and diffluence focused over the lower MS Valley. Similar broader scale flow and ascent will remain in place over the next few hours with continued potential for training/backbuilding existing across a wider region than just the New Orleans metro, though coverage of very high rainfall rates may be limited in scope. While flash flooding is ongoing across portions of southeastern LA, some uncertainty exists with the longevity of cells over the New Orleans metro given the potential for exhausting of instability. The development of additional flash flood producing rainfall across other locations is also a bit uncertain. While the setup favors rainfall rates over 3 in/hr expanding to the west and north of New Orleans, high flash flood guidance of 3 to 4+ inches per hour is in place for southern portions of the lower MS Valley so any additional flash flooding may be limited to urban locations where infiltration of water will be slowed. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8G6OZzvNq_ldcFlbDDjLfH4OGZv-aEDF8ByEBpIae-8YgYwJz-7j091BHtc47XqD7DcW= 4Bq_34cWEAIsE-a7Fjgu76A$ for graphic product... ATTN...WFO...JAN...LCH...LIX...MOB... ATTN...RFC...LMRFC...NWC... LAT...LON 32959013 32958936 32668890 31998885 30738906=20 29918927 29439021 29599150 29899210 30629233=20 31419172 32239112=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) .