Subj : Heavy Rain/Flooding FL To : All From : Dumas Walker Date : Wed Jun 12 2024 08:17 am AWUS01 KWNH 121216 FFGMPD FLZ000-121800- Mesoscale Precipitation Discussion 0427 NWS Weather Prediction Center College Park MD 815 AM EDT Wed Jun 12 2024 Areas affected...western (Gulf) coast of central and southern FL Concerning...Heavy rainfall...Flash flooding likely Valid 121215Z - 121800Z Summary...Localized rainfall rates on the order of 2-4"/hr may support additional localized totals of 6"+ with sufficient training/repeating of cells. Localized instances of flash flooding are likely, given the increased sensitivity from recent heavy rainfall. Discussion...Heavy shower activity is once again building over the warm waters of the southeast Gulf of Mexico, following a relative lull this morning in convective activity along the western coast of central FL. A 25-35 kt low-level jet (LLJ) is situated just downstream (with the maxima near the eastern central coast of FL), resulting in a localized enhancement of lift (via DPVA with minimal influence from upper-level dynamics). The mesoscale environment is reminiscent of the tropics, as PWATs of 2.0-2.5" are near record levels (per TBW sounding climatology) with dew points in the upper 70s to near 80deg F, ML CAPE of 1000-1500 J/kg, and effective bulk shear near 20 kts. While deep convection may be able to tap into more significant instability (as indicated by 3000-5000 MU CAPE just offshore), relatively shallow heavy showers/thunderstorms will easily produce 1-2"/hr rates (with more intense convection capable of 2-4"/hr rates, particularly if additional training/repeating occurs). Hi-res CAMs paint a rather concerning picture this morning, suggesting additional localized totals of 6"+ are possible through 18z. This is indicated by both the 06z HREF probability matched mean (PMM) QPF and 40-km neighborhood exceedance probabilities (40-70% for 5" exceedance), as well as by hourly runs of the HRRR since 06z. That said, not every HREF member or every run of the HRRR indicates such totals, as this threat is conditionally dependent on a training/repeating axis to set up along the coast. This could occur anywhere from Sarasota to Naples, though the Fort Myers/Punta Gorda region looks most favored (per the observational trends matching up quite well with guidance). Given that average totals over the past 24 hours commonly range from 3-5" (with localized totals remarkably as high as 6-12", per MRMS esitimates), isolated instances of flash flooding appear to be likely (with locally significant impacts possible in poor drainage, urbanized terrain). Churchill ATTN...WFO...MFL...MLB...TBW... ATTN...RFC...SERFC...NWC... LAT...LON 28188232 27958105 26628083 25558114 25978226 27288306 27968304 --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175) .