Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 24 2024 03:43:52 AWUS01 KWNH 240343 FFGMPD NCZ000-SCZ000-GAZ000-240800- Mesoscale Precipitation Discussion 0714 NWS Weather Prediction Center College Park MD 1143 PM EDT Tue Jul 23 2024 Areas affected...West-Central Georgia northeast into the Piedmont of North Carolina Concerning...Heavy rainfall...Flash flooding possible Valid 240342Z - 240800Z Summary...Training of showers and thunderstorms will persist overnight. Rainfall rates within this convection may reach 2"/hr at times, resulting in a corridor of 2-4" of rain and localized flash flooding. Discussion...The regional radar mosaic shows a line of expanding thunderstorms from near Columbus, GA northeast towards Raleigh, NC. This convection is firing along a surface trough draped along the Piedmont, leading to enhanced localized convergence. A weak mid-level perturbation lifting across GA is additionally providing ascent along this trough, while aloft some weak jet level divergence is positioned overhead. Together this is providing ample ascent into a corridor of 2000 J/kg MUCAPE and high PWs of 1.9-2.2 inches, above the 90th percentile for the date according to the SPC sounding climatology. The 00Z U/A sounding out of KFFC indicated steep lapse rates below 800mb, with a saturated column and freezing levels around 14,000 ft. This will support a hybrid Bergeron/warm rain process to drive rainfall rates that have been estimated above 1.5"/hr in ongoing convection. The high-res CAMs are struggling with the current activity, and only the FV3 has any real indication of the ongoing coverage. Even that is underdone, however, so the HREF probabilities are being negatively influenced by this lack of model support. The flash flooding concerns then are supported primarily by an ingredients based approach, with high PWs and persistent thermodynamic advection being supported by 850mb SW inflow of 15-25 kts along the periphery of a low-level theta-e ridge. With the Piedmont trough remaining in place through the evening, and the weak impulse lifting out of GA, this should allow for a continuation and even expansion of thunderstorms with 1-2"/hr rates. Although storm motions should remain progressive on 850-300mb mean winds around 20 kts, these winds parallel to the trough suggest an enhanced training risk as cells traverse continually to the northeast through the next several hours. Where coverage is most widespread and cells are most intense, likely downstream of the upper impulse, this could result in 2-4" of rain with locally higher amounts. Some of this area has been excessively wet the past 7 days as reflected by AHPS rainfall departures that are 300+% of normal. This has caused local reduction in FFG, especially along and west of the Fall Line, to be 1.5-2.5"/3hrs, which could be exceeded by these training storms. Otherwise, flash flooding is expected to be primarily isolated and in urban areas tonight, but anywhere these intense rain rates can train most effectively, flash flooding may occur. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7bNFyVqQSaPX3Q4Oc-IHOSGSrsPIPf7LPGDE5kxDXyxUa4NX6Ylu48bCH8Im1BCZG3w_= RYFieL-1WXYKRCas47fMTIo$ for graphic product... ATTN...WFO...AKQ...CAE...CHS...FFC...GSP...ILM...MHX...RAH... RNK... ATTN...RFC...SERFC...NWC... LAT...LON 36557731 36337707 35887731 35437766 34647878=20 33937988 33428075 32838189 32368298 32208409=20 32248437 32558441 33508368 34418203 35258085=20 35628020 36077952 36347907 36527831=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) .