Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 27 2024 02:34:33 AWUS01 KWNH 270234 FFGMPD VAZ000-NCZ000-SCZ000-GAZ000-TNZ000-270830- Mesoscale Precipitation Discussion 1071 NWS Weather Prediction Center College Park MD 1034 PM EDT Thu Sep 26 2024 Areas affected...northeastern GA into the western Carolinas and southwestern VA Concerning...Heavy rainfall...Flash flooding likely Valid 270230Z - 270830Z Summary...Additional 1-3 inch rainfall totals, with localized 3-5 inches into the Blue Ridge Mountains, are expected through 08Z across GA/SC/NC. Flash flooding is ongoing and will only worsen and expand with time. Discussion...Regional radar imagery from 0215Z showed widespread rain across much of the southeastern U.S. but with gaps over portions of SC in advance of an outer rain band from Helene tracking across the southeastern SC/GA border. A combination of MRMS and gauge reports showed peak rainfall rates ranging between 0.5 to 1.5 in/hr across the upslope favored terrain of the southern Appalachians, specifically the Blue Ridge Mountains. Instability remains low in the vicinity of the terrain, less than 250 J/kg (via 02Z SPC mesoanalysis data), increasing to over 1000 J/kg near the SC/GA coast. However, strong forcing, including 30-40 kt of southeasterly 925-850 mb winds (via KGSP and TCLT VAD wind data) was favorably oriented into the mountains, beneath divergent and diffluent flow aloft to the east of a closed low over southeastern MO and in advance of Hurricane Helene. No major changes to the current setup are expected through 08Z with the core of Helene perhaps just getting into the southern portions of the MPD threat area around 08Z. However, some increase in instability across inland is anticipated as Helene tracks northward overnight and an increase in the 925-850 mb wind into the 50-70 kt range overspreads the region. Rainfall rates of 0.5 to 1.5 in/hr at times will continue with an additional 1-3 inches for many areas from northeastern GA into central and western SC/NC with locally 3 to 5 inch additional totals for the terrain. These rains will continue to make for an extremely dangerous situation later tonight as the core of Helene's rainfall arrives later this morning, for which another MPD will be issued. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8507ghn4_OfQ0msZxABfsw7hon-pAhQj4dJCRsRRojdNrckPRvz-ZJgfoZjuT2HuVaWq= zTeXznXhxMAZ7LnLrC83l1s$ for graphic product... ATTN...WFO...CAE...CHS...FFC...GSP...MRX...RNK... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 36968025 36658015 36228066 34778055 33538070=20 32718117 32598203 32798287 33448393 34458474=20 35228414 36048240 36758121=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) .