Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Apr 25 2025 18:40:39 AWUS01 KWNH 251839 FFGMPD TNZ000-ALZ000-MSZ000-251840- Mesoscale Precipitation Discussion 0175 NWS Weather Prediction Center College Park MD 840 AM EDT Fri Apr 25 2025 Areas affected...portions north-central MS into northwestern AL and Middle TN Concerning...Heavy rainfall...Flash flooding possible Valid 251240Z - 251840Z Summary...Intensifying thunderstorm activity will support 3-6 hour localized totals as high as 3-5" through midday. Isolated to scattered instances of flash flooding are possible. Discussion...A cluster of thunderstorms is becoming more intense and organized this morning over portions of the MS Delta, supported by a mid-level shortwave/trough and enhanced low-level convergence (southerlies from the Gulf and westerlies over the Ark-La-Tex). While the influence of the subtropical jet to the southwest is waning relative to the past few days, the aforementioned shortwave is providing ample diffluence aloft as the area is situated between the polar and subtropical jets. Per SPC's SFCOA analysis at 12z, the mesoscale environment is characterized by SB CAPE of 500-1500 J/kg over MS (with 500 J/kg or less over north AL and Middle TN, but anticipated to increase), PWATs of 1.4-1.8 inches (between the 90th percentile and max moving average, per JAN sounding climatology), and effective bulk shear near 20 kts. The combination of moderate instability, highly anomalous moisture, and sufficient bulk shear should continue to maintain relatively organized convection. Hi-res CAMs are in relatively good agreement with regard to expected localized amounts going forward, with both the 06z HREF and 00z REFS probability-matched mean QPF indicating localized totals as high as 2-3" (though the exact placement of these higher totals varies quite a bit, as evidenced by 06z HREF and 00z REFS Ensemble Agreement Scale 1" exceedance probabilities of 10% or less). More recent runs (since 06z) of the HRRR have been quite a bit more robust with QPF, indicating totals as high as 3-5" through 18z (and the latest observational trends are supportive of this, as convection is beginning to locally train from southwest to northeast over portions of the MS Delta with MRMS hourly estimates near 2.5"). With much of this QPF expected to fall in as little as a 3-hr period, associated FFGs generally range from 1.5-3.0" (with 6-hr FFGs ranging from 3.0-5.0"). Isolated to scattered instances of flash flooding are possible. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4HV3v4pPP987NOVoFP8ZRSND8srVIJVosByvDaE5xv-cqIRjgNUL4e72jc_TVoCx-gUY= eQtrHTxNW75JIIpJ8tU3joI$ for graphic product... ATTN...WFO...BMX...HUN...JAN...MEG...OHX... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 35918727 35678623 34918587 33648730 32838905=20 32829082 33449104 34069020 34408980 35308870=20 =20=20=20=20=20=20=20=20=20=20=20=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) .