Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 14 2023 08:51:25 AWUS01 KWNH 140851 FFGMPD FLZ000-GAZ000-ALZ000-141445- Mesoscale Precipitation Discussion 0722 NWS Weather Prediction Center College Park MD 449 AM EDT Fri Jul 14 2023 Areas affected...FL Panhandle and surrounding portions of AL/GA Concerning...Heavy rainfall...Flash flooding likely Valid 140845Z - 141445Z Summary...Rainfall rates of 1-3"/hr will likely lead to additional localized totals of 3-6"+. Isolated to widely scattered instances of flash flooding are likely, and a significant instance or two of flash flooding are possible. Discussion...Convection has proliferated early this morning across the FL Panhandle and adjacent portions of MS/GA, located in the vicinty of a long-lived mesoscale convective vortex (MCV) that has slowly drifted southeastward from AR/LA/MS/AL over the past couple of days. A cluster of convection over Jackson/Holmes county in the FL Panhandle has been particularly impressive, continuously backbuilding into the 700 mb flow (where the effects of the MCV have been most pronouced during the past couple of flash flood events across MS/AL and AR/LA). While localized rainfall rates here have been pretty consistently 2-3"/hr for the past couple of hours, elsewhere realized hourly amounts have been closer to 1-2" (as cells have progressed towards the ESE with the 850-300 mb flow at 10-15 kts). The mesoscale enviornment is characterized by an ML CAPE gradient of 500-2000 J/kg (highest values farther west), precipitable water values of 2.2-2.4 inches (near the max moving average, per TLH sounding climatology), and veering ESE low-level (925 mb) flow of 15-20 kts. While effective bulk shear is quite minimal (less than 20 kts), continued low-level moisture transport with overrunning along the 305K isentropic surface should continue to maintain convection with additional backbuilding and repeating of cells remaining fairly localized. Expecting 1-3"/hr rainfall rates to continue through early to mid-morning, though the hourly runs of the HRRR since 00z have been quite inconsistent with the depiction of convective coverage. The 00z HREF probability matched mean QPF provides a more realistic picture overall, and even it was a notably too slow with initiating convection over the past few hours. That said, it seems reasonable to assume the 3-6"+ localized totals that it depicts through 15z will likely be realized, as this MCV has had a history of producing localized 6"+ totals during the late overnight and early morning hours over the past couple of days. While the relatively sandy soils of the FL Panhandle are generally able to take quite a bit of rain, these totals are still likely to overwhelm the infiltration potential, as much of this rainfall can occur over a period of only a few hours (and 3-hr FFGs are generally 3-4"). For these reasons, isolated to widely scattered instances of flash flooding are considered likely, and a significant instance or two of flash flooding is possible (particularly if these extreme totals occur over more vulnerable urbanized terrain). Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9CM2iAuC1r0LMeph5hZXuvKkoScZZper1V39UiM_xzyFTkM0b7cqZk61s9yg5Q7AdjXO= hfgJTitTCgWIVrWP3Pfgq3U$ for graphic product... ATTN...WFO...MOB...TAE... ATTN...RFC...SERFC...NWC... LAT...LON 31538571 31058426 30118459 29558515 30048605=20 30288716 30798767 31308726=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) .