Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 09 2025 19:10:52 AWUS01 KWNH 091909 FFGMPD NCZ000-SCZ000-FLZ000-GAZ000-100050- Mesoscale Precipitation Discussion 0630 NWS Weather Prediction Center College Park MD 308 PM EDT Wed Jul 09 2025 Areas affected...South-Central North Carolina through North Florida Concerning...Heavy rainfall...Flash flooding possible Valid 091907Z - 100050Z Summary...Widespread showers and thunderstorms will continue to drift slowly across the area through this afternoon. Rainfall rates of 2-3"/hr are likely, which could produce 2-4" of rain with locally higher amounts. This may result in flash flooding. Discussion...The experimental GOES-E day-cloud microphysics RGB clearly indicates the breadth of convection across coastal GA and SC this afternoon. Widespread and rapid blossoming of updrafts into anvils are noted in the satellite imagery, which is collocated with expansive reflectivity above 40dbZ on the regional radar mosaic. The quickness with which updrafts surge into Cb is indicative of the extreme environment, characterized by SBCAPE eclipsing 4000 J/kg and PWs measured by GPS exceeding 2.25 inches which is above the 90th percentile and approaching daily records. Into these thermodynamics, forcing for ascent is being driven by a pair of vorticity maxima approaching the region beneath increasing upper diffluence from the distant tail of a jet streak positioned to the northeast. Additionally, the sea breeze boundary and resulting outflow boundaries from convection are providing low-level ascent to sustain and regenerate thunderstorms. The 12Z U/A sounding from both KCHS and KJAX measured freezing levels around 15,500 ft, with weak and chaotic winds of 10kts or less through most of the column. This indicates that efficient warm-rain processes will dominate today, with slow and chaotic cell motions also expected. This is clearly evident already, and recent radar-estimated rain rates have exceeded 2"/hr from KCLX, leading to MRMS measured 1-hr rainfall above 2.5" in isolated locations over southeast GA. As low-level flow converges across the area, with increasing PW advection surging onshore (as reflected by the sfc-850mb CIRA LPW percentiles), and ascent persists into the additional moistening, rainfall rates will continue to intensify, with widespread rates above 2"/hr likely, and brief 4"/hr rates possible as shown on the HRRR 15-min rainfall reaching 1" in spots. Although bulk shear will be minimal so storms will remain of the pulse variety, collisions and mergers of cells could cause additional development into clusters at times. With weak flow throughout the column, storm motions will be chaotic and slow as dictated by these collisions/outflows, and upwind propagation vectors into any clusters collapse to around 0 kts suggesting net stationary motion at times. Where this occurs, total rainfall will likely (60%) exceed 3", with as much as 5" possible (15%) in a few locations. Although some parts of the coastal plain have received heavy rain the past 7 days, it has been very scattered, and NASA SPoRT 0-10cm soil moisture is generally normal to below normal. This has resulted in FFG that is generally 3-4"/3hrs, although likely lower across any urban areas. Despite that, 3-hr FFG exceedance probabilities reach as high as 20-30%, further indicating the potential for instances of flash flooding due to these slow moving storms into the evening. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_N50AuNE_ypbqvX5uXNzSJ9WLch0CK7gQjuOIkF0S1LbSiyv_ROhYmaFUdc9TSz92ds1= 4XVkl8ZIpECy9j-EYDiOGxI$ for graphic product... ATTN...WFO...CAE...CHS...FFC...GSP...ILM...JAX...RAH...TAE... TBW... ATTN...RFC...ALR...NWC... LAT...LON 35438047 35308008 35007979 34637962 34247968=20 33747995 32908028 32258059 31628104 30928129=20 30448135 30088131 29698134 29408239 30058303=20 31088356 32158331 33028304 33718254 34378210=20 34878173 35308127 35428093=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) .