Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Feb 11 2023 23:50:43 AWUS01 KWNH 112350 FFGMPD SCZ000-GAZ000-120548- Mesoscale Precipitation Discussion 0063 NWS Weather Prediction Center College Park MD 649 PM EST Sat Feb 11 2023 Areas affected...coastal Georgia & South Carolina Concerning...Heavy rainfall...Flash flooding possible Valid 112348Z - 120548Z Summary...Developing showers and thunderstorms are expected to continue to expand in coverage and intensity over the next several hours. Hourly rain totals to 2" with local amounts to 4" are possible. Discussion...The 2300 UTC observation set indicated that a low pressure system appeared to be forming just northwest of the Okeefenokee swamp in far southern GA. Divergence aloft is being sponsored by a cold low near the central Gulf coast. Recent indications via radar and satellite imagery showed increasing concentration of convective activity near the forming low, with some local hourly rain estimates up to 1". Other convection offshore SC closer to the coastal front has been edging closer to shore over the past couple hours. MU CAPE of 500-1000 J/kg exists near the low per SPC mesoanalyses. Precipitable water values have risen above 1.75" per recent GPS data. Effective bulk shear is 30-40 kts across coastal GA. Flow is nearly unidirectional out of the southwest. RAP guidance indicates that the low forming in southeast GA is expected to track northeast towards the central coast of SC over the next several hours, which would act to bring the coastal front closer to the coast, if not ashore, which would increase instability near and ahead of the cyclone. RAP guidance indicates MU CAPE reaching 1000+ J/kg ahead of the low, which would allow convection to be more robust, and potentially organize and train.=20 Low to mid-level frontogenesis is expected to overlap with the incoming instability from roughly Savannah northeastward, which would aid rainfall efficiency. There is a mild signal in the 18z HREF of a couple rounds of heavy rainfall, particularly near the lower and middle SC coast. While the guidance shows greater than average spread, the expected evolution favors heavy rainfall.=20 Hourly rain totals to 2" with local amounts to 4" are seen on a couple pieces of mesoscale guidance, and befit the environment expected to evolve this evening into tonight. Some of this region has seen rainfall of 100-200% of average over the past week, but the region is also marshy/swampy. Heavy rain issues should be more significant/evident in urban areas. Considering the model dispersion, confidence is lower than average. Roth ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!498AThTBTnvjevzpUlh069BYRG5cKa9oFpmI85P8xbd5jIcwRIjdOdV9A3enaEvZa8EJ= BmgVc-BqitcyMOYV8oF-3VM$ for graphic product... ATTN...WFO...CHS...ILM...JAX... ATTN...RFC...SERFC...NWC... LAT...LON 33367975 33207909 31958082 30998144 31108246=20 32678141=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) .