Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Mar 25 2023 08:27:42 FOUS30 KWBC 250827 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 426 AM EDT Sat Mar 25 2023 Day 1 Valid 12Z Sat Mar 25 2023 - 12Z Sun Mar 26 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Wegman Day 2 Valid 12Z Sun Mar 26 2023 - 12Z Mon Mar 27 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. ....Southeast... A stalled out frontal boundary will be draped across the Southeast from northern Louisiana into the Carolinas Sunday. This front will act as a focus for convection across this region. However, other than the surface front itself, there's very little if any additional forcing that will work to organize and strengthen any convection that develops along the front. Thus, expect pulse and multicellular clusters to be the dominant convective modes. With the up to 1.500 J/kg of MUCAPE and PWATs to 1.5 inches the likelihood of locally heavy rainfall is moderate across this region. However, while the storms will be capable of producing heavy rainfall, their disorganization will keep the coverage of heavy rainfall rather low. Flash flood guidance is exceptionally high across this area, owing to the recent dry weather. NASA Sport shows soil moisture to average about 10-20% saturated, especially from central AL eastward. Any storms would need to produce 2.5-3.0 inches per hour in order to exceed that guidance, and more than that for 3 and 6 hour FFGs. This is highly unlikely to occur, due to both storm motion, disorganization, and unfavorable antecedent conditions. If several rounds of storms happened to go over any one area, one flash flooding event isn't entirely out of the question, but it was determined that this scenario is highly unlikely, and would fall in the 0-5% sub-Marginal risk. Thus, despite the heavy rainfall threat, it's highly unlikely that heavy rainfall will translate to flash flooding. In coordination with BMX/Birmingham, AL, MOB/Mobile, AL, GSP/Greenville-Spartanburg, SC, CHS/Charleston, SC, and ILM/Wilmington, NC forecast offices, all unanimously agreed that the lack of forcing and very high FFGs will all but certainly eliminate the flash flooding threat in this area. Thus, the inherited Marginal Risk area was downgraded to a risk-free map with this morning's update. Wegman Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8QGD0hMJmJxfyLq1oo2v403703R7mYR-gmKwDyTEtwWS= IX_JgWHEbocAGQPElfRzbLafxuM7bXjpRtAzlLyat332rz0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8QGD0hMJmJxfyLq1oo2v403703R7mYR-gmKwDyTEtwWS= IX_JgWHEbocAGQPElfRzbLafxuM7bXjpRtAzlLyaR8Mqwyc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8QGD0hMJmJxfyLq1oo2v403703R7mYR-gmKwDyTEtwWS= IX_JgWHEbocAGQPElfRzbLafxuM7bXjpRtAzlLyaduLF6CI$=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .