Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 25 2025 15:29:43 AWUS01 KWNH 251529 FFGMPD SCZ000-GAZ000-252130- Mesoscale Precipitation Discussion 0313 NWS Weather Prediction Center College Park MD 1129 AM EDT Sun May 25 2025 Areas affected...Lowcountry of South Carolina, Southeast Georgia Concerning...Heavy rainfall...Flash flooding possible Valid 251530Z - 252130Z Summary...Thunderstorms will expand and intensify across the Lowcountry of South Carolina and coastal plain of Georgia through the afternoon. These storms will move slowly and chaotically at times, allowing for 2-3"/hr rates to produce as much as 3-5" of rain. Flash flooding is possible. Discussion...The GOES-E day-cloud phase RGB late this morning shows rapid expansion and intensification of updrafts associated with increasing coverage of convection noted on the regional radar mosaic. This activity is blossoming in response to an MCV, likely a remnant from convection yesterday over the Ozarks, moving across South Carolina, while a shortwave and accompanying surface low tracks across Georgia. Additional forcing for ascent is being provided via convergence, both along a slowly advancing warm front, and through sea breeze interactions. This ascent is acting upon extremely favorable thermodynamics characterized by PWs analyzed by the SPC RAP of 1.7 to 1.9 inches, above the 90th percentile for the date, and expanding SBCAPE above 3000 J/kg. Where the strongest ascent is overlapping these most impressive thermodynamics, rainfall rates have been estimated via KCLX to exceed 2.5"/hr. As the afternoon progresses, the high-res CAMs are in good agreement that convection will expand across eastern GA and southern SC as forcing for ascent increases in response to the movement of the shortwave and warm front into the area. This will act upon thermodynamics that will remain extremely robust, supporting rainfall rates that may approach 3"/hr at times as noted via both HREF and REFS probabilities for 2"/hr exceeding 30%. Although shear is minimal, which will likely limit storm organization, these rates could become problematic as storms track extremely slowly through the aftn. This will be due to generally weak 0-6km mean winds of just around 10 kts to the east, being impeded by the westward advance of the sea breeze boundary within the weakly forced environment. This will result in the collapse of Corfidi vectors to 5 kts or less, suggesting nearly stationary storms or chaotically moving storms. With rain rates expected to remain 2-3"/hr, this could produce 3-5" of rain in some areas. Rainfall across the region has been minimal as of late, reflected by both AHPS rainfall departures and NASA SPoRT soil moisture, which has resulted in elevated FFG that is generally 3"/1hr and 4"/3hrs. Despite that, modest FFG exceedance probabilities do exist among the ensemble systems, further indicative of the intense rainfall potential. While flash flooding impacts will be most likely across urban areas, anywhere storms linger or repeat could experience flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9DLkYv3UfhzPax8FzGSVG40XByARSD3hJqCbX4HLpyJJhPgsdAysjcKd2Sn_Lr55-5-s= WqoGaRBLj0MXQ9HNJu0W5IU$ for graphic product... ATTN...WFO...CAE...CHS...FFC...JAX...TAE... ATTN...RFC...ALR...NWC... LAT...LON 33568094 33538039 33397992 33247959 32987960=20 32677989 32428023 32118065 31768098 31508131=20 31458190 31458286 31628335 31908333 32368308=20 32758280 33268215 33438162=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) .