Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 11 2025 05:17:59 AWUS01 KWNH 110517 FFGMPD NCZ000-SCZ000-GAZ000-111115- Mesoscale Precipitation Discussion 0902 NWS Weather Prediction Center College Park MD 116 AM EDT Mon Aug 11 2025 Areas affected...Coastal Georgia through Coastal Southeast North Carolina Concerning...Heavy rainfall...Flash flooding possible Valid 110515Z - 111115Z Summary...Heavy showers and isolated thunderstorms pivoting onshore will continue overnight. Rainfall rates of 2-3"/hr are likely, which through training could produce 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this evening shows expanding convection lurking just offshore to the east of the SC and GA coasts. This convection is expanding in response to ascent driven via strung-out vorticity aligned along the coasts combined with increasing thickness diffluence noted in the mid-level thickness fields. At the same time, 850-500mb winds are generally from the E/SE around a mid-level trough axis, with recent 850mb winds measured at KJAX and KCLX VWPS of 20-30 kts, more than twice the mean wind, supporting additional ascent. This lift is occurring into impressive thermodynamics characterized by PWs measured by GPS of 2.3 to 2.4 inches, nearly the daily record for the region, overlapping MUCAPE of 1000-3000 J/kg as analzyed by the SPC RAP. Together, this is resulting in an expansion of heavy rainfall with embedded thunderstorms, with impressive reflectivity above 40dBZ identified near shore via the regional radar mosaic, but also additionally farther offshore utilizing the satellite GREMLIN product, with sufficient GLM lightning density to support its output. As onshore flow persists and forcing remains, convection should expand and intensify through the night. As is typical with nocturnal flare ups like as expected, the heaviest rainfall should be confined to offshore and the immediate coast due to a rapid dropoff in instability inland. The simulated reflectivity and rainfall footprint from the available CAMs supports this conceptual model, but with 850mb winds continuing to exceed the mean wind, some inland push of heavier rainfall is possible. However, the most intense rain rates, which have a 15-25% chance of exceeding 2"/hr from the HREF, and may locally exceed 3"/hr at times (15-min HRRR rainfall of 0.75") should remain along the immediate coast. Despite storm motions of 10-15kts to the NW, Corfidi vectors collapsed to 5 kts or less and aligned against the mean wind indicate backbuilding and repeating cells will rotate onshore to enhance the duration of rainfall. Where this occurs, total rainfall through morning will likely reach 2-3". with local amounts as much as 5" possible. 3-hr FFG from the Georgia coast northeast into the Grand Strand is generally 2-3"/3hrs, although is locally compromised to as low as 1.5"/3hrs due to 24-hr MRMS measured rainfall of 3-5". While the flash flood risk appears generally isolated, should any of these training bands occur atop these more vulnerable soils, or into any more urbanized areas, flash flooding would become more likely overnight. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7BGhqHsZ-MdeMYOjwksyB6wdTCG6tK8QRWAaO1NuzEL4UrP7pKXRdmJBBUplSxbdGUq6= ab1_mirvjP-0jKM5Wxfv-Z0$ for graphic product... ATTN...WFO...CHS...ILM...JAX... ATTN...RFC...ALR...NWC... LAT...LON 34347830 34227783 33877777 33527829 33177880=20 32887920 32188020 30948101 30848140 30988167=20 31328190 31658176 31968150 32188132 32488103=20 32868069 33318020 33877959 34207906=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .