Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 28 2024 16:50:03 AWUS01 KWNH 281649 FFGMPD NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-282230- Mesoscale Precipitation Discussion 0748 NWS Weather Prediction Center College Park MD 1249 PM EDT Sun Jul 28 2024 Areas affected...Southern Appalachians into the Piedmont of Georgia Concerning...Heavy rainfall...Flash flooding possible Valid 281647Z - 282230Z Summary...Showers and thunderstorms expanding within a destabilizing environment will become widespread through the afternoon. Rainfall rates in the most intense convection will likely reach 2-3"/hr, which through slow storm motions could result in 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this afternoon reflects an expansion of showers and thunderstorms across much of northern Georgia beneath increasingly agitated Cu and TCu noted in the GOES-E visible imagery. Radar-estimated rainfall rates within this blossoming convection have exceeded 1"/hr via KFFC WSR-88D, and storm motions are only around 5 kts to the E/NE. This activity is being fueled by robust thermodynamics characterized by PWs measured by the 12Z FFC U/A sounding of 2.13 inches, well above the 90th percentile for the date, with 14,000 ft freezing levels and almost 1500 J/kg of SBCAPE through a deep layer of weak, moist adiabatic lapse rates favoring efficient warm-rain processes. Into this environment, forcing for ascent is being provided by moist isentropic ascent as 850mb flow veers out of the south to lift atop a warm front and wedge centered to the east, aided by upslope flow into the higher terrain. Additionally, an upper jet streak intensifying beneath a synoptic trough over MO will gradually impinge into the area this afternoon increasing upper level diffluence. The recent runs of the HRRR and RRFSp1 both indicate that this region will experience multiple rounds of convection through the evening. Initially, pulse-type thunderstorms are expected to develop within the weak bulk-shear but favorable overlap of ascent/thermodynamics. These should expand across N GA and then lift slowly N/NE on weak 0-6km mean winds of just 5-10 kts and along an impressive CAPE gradient west of the wedge of high pressure. With elevated PWs persisting and even increasing, rainfall rates of 2-3"/hr are possible as reflected by HREF probabilities for 2"/1hr reaching 30-40%, and 15-min HRRR accumulations approaching 0.75". Multiple rounds of these slow moving thunderstorms could produce 2-3" of rain in some areas as shown by HREF 6-hr neighborhood probabilities. Additionally, convection blossoming to the west this afternoon is progged to push eastward this evening, and while this should be more progressive owing to the increase and veer of the low-level winds, it could add additional rainfall leading to event-total rainfall as much as 5" in some areas. The Southern Appalachians and surrounding Piedmont of GA have been wet recently which has yielded NASA SPoRT 0-10cm RSM of around 60% and accompanying compromised FFG as low as 1.5"/1hr and 2-2.5"/3hrs. Both the NWM ROFs probabilities and HREF 3-hr FFG exceedance probabilities suggest instances of flash flooding are possible due to these rounds of heavy rain through this evening, but are most likely across any urban areas or most sensitive terrain features. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_zULQVvfSx87UFIgITJ63nrgEaZDMGxClnvRrLJQE_Myc4eeg4l8r99Yx_adurr6_LU0= MApAckJDM3zhkFVftEq5qmg$ for graphic product... ATTN...WFO...BMX...FFC...GSP...HUN...MRX...OHX... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 36268381 35908317 35248275 34788294 34308316=20 33518317 33178341 32998442 33338549 34228624=20 34898570 35778500 36238455=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) .