Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Dec 26 2023 05:57:42 AWUS01 KWNH 260556 FFGMPD NCZ000-SCZ000-GAZ000-TNZ000-261155- Mesoscale Precipitation Discussion 1221 NWS Weather Prediction Center College Park MD 1255 AM EST Tue Dec 26 2023 Areas affected...Piedmont into the southern Appalachians Concerning...Heavy rainfall...Flash flooding likely Valid 260555Z - 261155Z Summary...Areas of flash flooding are expected to develop across the southern Appalachians into the adjacent Piedmont through 12Z. Persistent moderate to heavy rain with peak rainfall rates of 0.5 to 1.0+ in/hr at times will likely lead to an additional 1-3 inches of rain through 12Z. Discussion...Rainfall across the southern Appalachians has been reported in the 2 to 5+ inch range over the past 12-24 hours. As of 0530Z, areas of moderate to heavy rain were ongoing across the region and are expected to persist through the rest of the night. SSE 925-850 mb winds of 25-40 kt were ongoing ahead of a 925-850 mb low/trough located in southeastern AL at 05Z, focused perpendicular to the axis of terrain from northern GA into western NC. While instability was weak, precipitable water values of 1.0 to 1.3 were present across the region, resulting in fairly persistent moderate to heavy rainfall with rates occasionally over 0.5 in/hr. 925-850 mb winds are expected to remain from the SSE/SE through the night but with an increasing magnitude toward 12Z as the 925-850 mb low/trough moves northeastward. In addition, a 150-180 kt upper level jet streak over the Lower Mississippi Valley is forecast by the RAP to edge northeastward through 12Z, with increasing left exit region ascent occurring over the southern Appalachians. The combination of these factors will support increased lift and rainfall coverage across the region, especially across northern GA into far western SC. Repeating showers and thunderstorms will be likely along with areas of training. Instability is forecast to remain weak overnight but increase into the 500-1000 J/kg range over portions of northern GA through 12Z, supporting the potential for higher rates, perhaps 1.0+ in/hr. Meanwhile, instability of less than 250 J/kg is expected to limit rain rates for much of western NC into adjacent portions of northern SC but still allow for an additional inch or so through 12Z. Due to rainfall that has already fallen and the expectation for an additional 1-3 inches of rain through 12Z, flash flooding is expected to become increasingly likely overnight. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-F1RpfUeL4BdSVghP6Ek6xw39E7CgpZaJeBTYHN9t1qWehBAVHpO7WLQkyAEymWUIeRw= Y2arlI5FpTnuVT33wffAfyQ$ for graphic product... ATTN...WFO...CAE...FFC...GSP...MRX...RNK... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 36528140 36438094 35718096 35268133 34388223=20 33888258 32908362 33278491 34588487 35338403=20 35758283=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) .