Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Mar 23 2025 22:06:13 AWUS01 KWNH 232206 FFGMPD TNZ000-ALZ000-MSZ000-ARZ000-240400- Mesoscale Precipitation Discussion 0079 NWS Weather Prediction Center College Park MD 605 PM EDT Sun Mar 23 2025 Areas affected...Western & Middle TN...Northern MS...Northwest AL... Concerning...Heavy rainfall...Flash flooding possible Valid 232205Z - 240400Z SUMMARY...Multiple rounds of intense showers/thunderstorms with rates of 1-1.5"/hr may allow for a few streets of repeating cells and 2-3" localized totals nearing/exceeding FFG values resulting in possible widely scattered incidents of low-end flash flooding, particularly near urban centers. DISCUSSION...GOES-E WV suite depicts a strong, compact short-wave across N IL/S WI moving quickly east with a lower-scale wave/mid-level trough accelerating eastward into the upper-Ohio River Valley. This is accompanied by a strong upper-level jet streak that has rounded the base of the main trof with solid right entrance ageostrophic response across the lower Ohio Valley providing strong divergence along and south into the Tennessee River Valley.=20 Surface and LLJ has responded with increasing Southwesterly flow fluxing higher theta-E air northward with Tds into the upper 50s and lower 60s. Filtered insolation and mid-level steepening lapse rates have made the area modestly unstable with MLCAPE nosing across W KY into W TN over 1000-1250 J/kg, along and ahead of solid cold front. Additionally, GOES-E Vis and sfc to boundary layer streamlines suggest a confluence axis between deeper Gulf moisture from the Western Gulf and return from the central/eastern Gulf becoming increasingly confluent across central MS to NE MS into Middle TN. With conditionally unstable air, this has been sufficient to break out weaker but slowly increasing convective activity across Middle TN... with some convection/flux convergence supporting rates of .5-.75", which is expected to increase over the next few hours. Forward propagation is likely to limit overall totals with any individual cell, but could be stage setting for later development. As the line expands, cells will have capability for back-building/flanking line development that is probable to align with strong/fast steering flow resulting in some accidental training. However, further upstream cold front is starting to advance with solid 90 degree convergence along the leading edge southwesterly LLJ/moisture plume. Cells will expand in coverage and width and should be capable of 1-1.5"/hr rates as they advance, with similar very fast (40+ kt) forward speed, likely limiting overall rainfall totals. Hence, any flash flooding potential will require these cells to traverse areas already affected by 1-2" totals with earlier rounds. If so, 2-4hr spot totals of 2-3" are possible. This is in range of the lower FFG values over the TN valley (1.5-2"/hr & 2-3"/3hr). As such, a few widely scattered instances of flash flooding are considered possible particularly after 00z and in/near urban settings. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5qS4wqKO0XRxof-tpw08nyp5JjttqzzEKkAI-JFPw30tXIEzHdpdsUsi4_LyUGI1LFvE= ooBcRUDKd0DxmmOzIwDWIKM$ for graphic product... ATTN...WFO...BMX...HUN...MEG...OHX... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 36488810 36478551 35158602 34288698 33908848=20 34009006 34279071 34979061 35638953=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) .