Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Apr 09 2023 18:46:46 AWUS01 KWNH 091846 FFGMPD FLZ000-100040- Mesoscale Precipitation Discussion 0174 NWS Weather Prediction Center College Park MD 246 PM EDT Sun Apr 09 2023 Areas affected...southeastern FL Concerning...Heavy rainfall...Flash flooding possible Valid 091844Z - 100040Z Summary...Localized flash flooding will be possible across the southeastern FL Peninsula this afternoon and early evening. Multiple rounds of thunderstorms with high rates may generate spotty totals in excess of 3-5 inches over a short period of time. Discussion...18Z visible satellite and surface observations placed a moderate strength cold front with a somewhat diffuse leading edge from Palm Beach to Collier County, sinking southward. Scattered thunderstorms were noted on local radar imagery near the front, with an average movement from the WNW at 10-20 kt. Additional convective development was in the early stages of development noted along a southern sea breeze boundary over southern Miami-Dade County. SPC mesoanalysis data from 18Z showed MLCAPE of 1000-1500 J/kg and precipitable water values between 1.5 and 1.7 inches over the southern third of FL, a couple of tenths higher than 12Z RAOBs from TBW and MFL. 925-850 mb winds were from an atypical N to NW in advance of the front but weak, only ranging from 5-10 kt. The environment is supportive of locally heavy rain, but there remain some questions as to specific magnitude, location and coverage of the heaviest rain. Current thinking is that upstream storms, currently southwest of Lake Okeechobee, will migrate ESE toward the Miami-Fort Lauderdale metro over the next 1-2 hours. Additional development in advance of this activity remains possible with an advancing outflow over Broward and TCu over south-central Miami-Dade counties. While weak, similarly oriented northwesterly 850 mb flow and steering flow could allow for repeating and short term training of cells, converging across the urban corridor of the southeastern Peninsula. Rainfall rates of 1-2 in/hr will be common, but slower movement and brief training of storms could easily support 2-3 in/hr rainfall rates. The HRRR has been fairly consistent with 6-hr rainfall totals of 4 to 8 inches, localized over the MIA/FLL metro. While this could be overdone in magnitude and misplaced, there appears to be a good signal for locally very heavy rain across portions of southeastern FL from the 12Z HREF with 20-25 percent probabilities for 5+ inches between 18-00Z. Despite fairly dry antecedent conditions, these high rainfall totals over a short period of time could result in localized areas of flash flooding. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6UD_BFyH6ZhHe_PGGJWErXPfCllVUKWqDjAIz3B05g-FXWFhmZgS6GGh3Jbe8LgobR27= 0OmQysr_H5QC1QbdSyFySpI$ for graphic product... ATTN...WFO...KEY...MFL... ATTN...RFC...SERFC...NWC... LAT...LON 26887993 26387976 25507998 25318010 25358053=20 25488059 26078043 26648039 26868033=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) .