Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 28 2024 18:23:04 AWUS01 KWNH 281823 FFGMPD FLZ000-GAZ000-290000- Mesoscale Precipitation Discussion 0749 NWS Weather Prediction Center College Park MD 222 PM EDT Sun Jul 28 2024 Areas affected...Florida Big Bend through the Central Florida Peninsula Concerning...Heavy rainfall...Flash flooding possible Valid 281821Z - 290000Z Summary...Showers and thunderstorms will rapidly increase in coverage through the afternoon. Rainfall rates may reach as high as 4"/hr for brief periods, resulting in pockets of 3-5" of rain with isolated higher amounts possible. This could result in flash flooding. Discussion...The regional radar mosaic this afternoon shows thunderstorms beginning to expand across the northern Florida Peninsula, with additional development occurring on sea breeze boundaries along the Atlantic coast, as well as the eastern Panhandle. These storms are developing in the vicinity of a stationary front wavering across northeast FL, with all low-level convergent boundaries driving sufficient ascent for convective initiation. The thermodynamics across the state are extreme, characterized by PWs of 2.25-2.5 inches, and SBCAPE of 3000-4000 J/kg. The morning soundings from JAX and TBW indicates deep saturation within the column from the surface to 200mb, with freezing levels nearing 16,000 ft to support efficient warm rain processes, and this is already materializing as radar-estimated rain rates above 2"/hr according to KJAX WSR-88D. As the afternoon progresses, the high-res CAMs are in good agreement that convection will rapidly expand south of the stationary front and along sea breeze boundaries. 0-6km bulk shear will remain minimal at least than 20 kts, which suggests storm mode will be pulse through the evening. However, with PWs near 2.5", SBCAPE potentially exceeding 4000 J/kg, and storm motions of just 5 kts, any storm collisions or boundary interactions will result in additional development of thunderstorms. Rainfall rates within this convection have a 70-80% chance of exceeding 2"/hr according to HREF neighborhood probabilities, while the 15-min HRRR accumulations exceed 1" in some areas suggesting that short-duration rain rates above 4"/hr are possible. Although each cell may have a short temporal duration in the pulse environment, these rates could still produce 1-3" in less than an hour, and any location that receives multiple storms has a 30-50% chance of accumulating more than 5" of rain through this evening. FFG remains high across the state at 3-4"/3hrs, but impressively the HREF exceedance probabilities peak above 50% for this threshold. This further reflects the intensity of the rainfall this afternoon. Additionally, much of the Panhandle and northern half of the Peninsula has received more than 150% of normal rainfall the last 7 days, further increasing the vulnerability of the soils to rapid runoff. Where any of these intense rain rates occur across urban areas, or where multiple rounds can occur across the more sensitive areas, instances of flash flooding could result. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4LrkCLvF6lxGzz_p_wSbH01Yxr9X9MUuKi6DrnDVOt5H2CUbmi-y7t8VoGeE5o_cwXIa= h9GkHOAEET_UtiiNWHNqvt4$ for graphic product... ATTN...WFO...JAX...MLB...TAE...TBW... ATTN...RFC...SERFC...NWC... LAT...LON 30738385 30698288 30538208 29958129 29148076=20 28008046 27538037 27318050 27248077 27298106=20 27528136 28148178 28668229 29088283 29538332=20 29988405 30078456 30108502 30128534 30368543=20 30618498=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) .