Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 20 2023 20:26:42 AWUS01 KWNH 202026 FFGMPD NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-210030- Mesoscale Precipitation Discussion 0773 NWS Weather Prediction Center College Park MD 426 PM EDT Thu Jul 20 2023 Areas affected...Northern AL...Northern GA...Southern TN...SW Upstate SC... Concerning...Heavy rainfall...Flash flooding possible Valid 202025Z - 210030Z SUMMARY...MCS with linear training band and potential for upwind back-building continues to sag southward into N AL/N GA. Still some potential for localized 2-3"/hr totals and spots up to 4" though early evening for possible flash flooding. DISCUSSION...Regional RADAR mosaic depicts and surface analysis depicts stronger cold pool developed over Middle TN and surged the southern flank of the deeper moisture convergence band south into the last row of TN counties entering NE AL and N GA; which is starting to slip out of MPD 771. MCV continues to be progressive but also remains further north along the KY/TN boarder and with the meso-high ridging across the southern Appalachians may result in a flattening of the upwind edge of the cold pool surge across N AL into N GA.=20 Upwind across NE MS/N AL, there is a solid reservoir of uncapped to very weakly capped of 3000-3500 J/kg of MLCAPE given low 90s temps and upper 70s Tds. Total moisture along/ahead of the flattening convergence axis is also well above 2" nearing 2.3" in spots, allowing for continued efficient warm cloud processes and rainfall rates of 2-3"/hr. VWP out of HTX also supports a weak backing of the 850mb flow, suggesting continued low-level confluence and ascent over the outflow boundary allowing for additional upstream redevelopment across N AL over the next few hours. The winds are only about 15kts and given the oblique angle of ascent, thunderstorms may be more scattered in nature but the potential remains sufficient for new development to once again align favorably parallel to deeper layer steering for training thunderstorm profiles. Given simlar efficient rates of 2-3"/hr; spots of 3-4" totals are probable across the area of concern.=20 While FFG values increase crossing the TN boarder into N AL/GA, there is enough complex terrain at the base of the Cumberland Plateau, western slopes of the Appalachians to be concerned for increased/faster runoff and flash flooding conditions. Given the higher FFG and higher uncertainty for upwind development flash flooding is considered possible over the evening hours.=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_wyIrA3FCUTuBNPyqbQC6sbhEc2qWpVFq9_Cf8F9iiuSxU2D0apB8RNvkKBWJgv-Sif9= pDWAHjExPUbuJY5o6p4Vw5w$ for graphic product... ATTN...WFO...BMX...FFC...GSP...HUN...MRX...OHX... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 35588667 35278427 34628274 33888280 33748384=20 34008533 34268620 34788711=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) .