Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 09 2024 21:59:11 AWUS01 KWNH 092159 FFGMPD FLZ000-ALZ000-MSZ000-LAZ000-100257- Mesoscale Precipitation Discussion 1169 NWS Weather Prediction Center College Park MD 458 PM EST Mon Dec 09 2024 Areas affected...Parts of Southeast LA, Southern MS, and Southwest AL Concerning...Heavy rainfall...Flash flooding possible Valid 092157Z - 100257Z SUMMARY... A weakening line of showers and storms as well as reforming convection upstream over south-central LA may lead to additional chances for localized flash flooding this evening along sections of the central Gulf Coast. DISCUSSION... Same shortwave responsible for the breakout of morning convection across southern LA is now crossing the central Gulf Coast and entering the Southeast, while strong uniform southwesterly flow continues to advect tropical moisture from the eastern Pacific per GOES-West ADV LPW. PWs remain in the 1.6-1.9" range per SPC's mesoanalysis and around the 90th climatological percentile. These elevated PW values continue to advect further eastward and across AL, but with instability remaining mostly meager. SBCAPE values have climbed to above 1000 J/kg across south-central LA mainly due to diurnal heating, which will wane in the next few hours. However, speed maxes noted in GOES-East ML WV exiting northern Mexico within the deep tropical moisture stream imply convection may continue to linger a few hours past sunset. This combination of elevated moisture, strong uniform southwesterly flow, and remaining instability pool will lead to additional chances for localized training thunderstorms capable of containing hourly rainfall rates up to 2"/hr through around 9 pm CT. A corridor of 3-5" of rainfall has already fallen per MRMS in a SW-NE oriented line along the northern shores of Lake Pontchartrain and southwestward. Otherwise, additional localized corridors of 1-1.5" have already occurred. Therefore, even though 3-hr FFG remains widely above 2.5" there could be localized areas more susceptible to flash flooding with 2-3" additional totals. Urban locations will be most at risk within the broader isolated flash flooding threat stretching from southern LA to southern MS. Farther east into southern AL, a continuous band of rainfall containing hourly rates around 1" is expected to continue within a corridor of enhanced atmospheric moisture and very low instability. This region may see more widespread rainfall amounts above 1.5", but falling at lower rates. Any flash flood risk for AL is considered low, with urban and poor drainage locations most at risk for isolated impacts. Snell ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_5mD1sgdjdxSJQUq--ZU_lFvtM-hwSmOEBRUzFgHv9etbNUToQBgD0D22VOt_sV5YVQq= _eYBHEVqLVb4zGcYLULQXZA$ for graphic product... ATTN...WFO...JAN...LCH...LIX...MOB... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 31828764 31668652 30968662 30388839 29879017=20 29609171 29979218 30519198 31059089 31578904=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) .