Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Nov 20 2022 10:27:25 AWUS01 KWNH 201027 FFGMPD FLZ000-201625- Mesoscale Precipitation Discussion 1125 NWS Weather Prediction Center College Park MD 525 AM EST Sun Nov 20 2022 Areas affected...Urban Corridor of Southeast FL Concerning...Heavy rainfall...Flash flooding possible Valid 201025Z - 201625Z SUMMARY...Slow-moving areas of heavy showers this morning are expected, and this may result in a localized urban flash flood threat. DISCUSSION...An uptick in convergent, moist low-level flow is expected this morning across coastal areas of southeast FL which will help set the stage for increasing shower activity, and a concern for locally heavy rainfall. Surface observations show evidence of a surface trough becoming a bit better defined just offshore of Biscayne Bay and toward the northwest Bahamas, and the latest HRRR guidance indicates this boundary drifting slowly off to the west this morning into the urban corridor from near Fort Lauderdale southward down through Miami and Homestead. The latest RAP analysis shows a strengthening instability gradient aligning itself with this surface trough, and radar imagery does show an increasingly concentrated area of heavy showers beginning to focus east of Biscayne Bay along this instability axis. Meanwhile, the RAP analysis is also showing a bit of an uptick in divergent flow aloft over the southern part of the FL Peninsula given proximity to the right entrance region of the subtropical jet crossing the Gulf of Mexico and the interior of the Southeast. This subtle deeper layer forcing through the column combined with the low-level moisture convergence/forcing and related instability concentrations near the southeast FL coastline is expected to facilitate slow-moving and locally focused areas of heavy showers this morning. The PWs are forecast to gradually rise to over 1.75 inches, especially after 12Z, and the latest CIRA-ALPW data shows already a robust degree of moisture concentrating in the lower levels of the column and including the 850/700 mb layer where stronger omega/forcing is expected to ensue. This should consequently result in convection that is efficient in nature and capable of heavy rainfall rates. The HRRR guidance and earlier HREF suite of the CAMs suggest 2+ inch/hour rainfall rates will be possible this morning. Given the slow-movement of the cells generally off to the west, these heavy rains will threaten the urban corridor of southeast FL, with locally as much as 3 to 5 inches of rain possible by late morning. In fact, recent runs of the HRRR are even a tad wetter. Consequently, there may be at least an urban flash flood threat that materializes over the next several hours. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9pKp5U8c8ypOV1BsaSVdjAjzLIHb6j6sp24HzxGzPXmWEWPYnDpSRwCKcsmE-y0h1gKv= Vq185FATy7GQMA88og188jU$ for graphic product... ATTN...WFO...KEY...MFL... ATTN...RFC...SERFC...NWC... LAT...LON 26188022 26188008 25998008 25718016 25518017=20 25278030 25298047 25558050 25948040=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) .