Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Nov 14 2023 23:28:04 AWUS01 KWNH 142328 FFGMPD FLZ000-150400- Mesoscale Precipitation Discussion 1171 NWS Weather Prediction Center College Park MD 626 PM EST Tue Nov 14 2023 Areas affected...Southeast FL Concerning...Heavy rainfall...Flash flooding possible Valid 142325Z - 150400Z Summary...Slow moving convection may pose an urban flash flood risk this evening across portions of Southeast Florida. Discussion...Convective intensity has increased over the past couple hours across eastern Broward County and southern Palm Beach County in southeast Florida. Latest mesoanalysis actually shows CAPE to be on a decreasing trend, and low level convergence to be steady. So the reason for the recent uptick is not immediately evident, which does make forecasting it's evolution over the next several hours a low confidence forecast as well. Forecast soundings earlier today did show a mid level dry layer, and recent WV imagery does seem to show some moistening in that level...so it is possible that this slight uptick in low to mid level moisture was enough to get deeper convective development. Regardless of the exact reason, we do have deep convection, and with easterly flow in the low levels and westerly flow aloft, this activity has not been moving much, focusing along the coastal convergence axis. In addition to the slow movement of cells, this activity is also likely to be efficient at rainfall production. The freezing level is at around 600 mb, and forecast soundings show the strongest lift is generally within the sfc-600mb layer. This overlap of strong lift within the above freezing cloud layer of the storm suggests efficient warm rain processes are in play. This supports the potential of 2-3"/hr rainfall where cells persist. As mentioned above, confidence on how this activity evolves over the next few hours is low. Most model guidance would suggest convection begins to weaken fairly soon, which is probably the most likely outcome. However, not seeing much sign of a weakening trend in radar or IR imagery, and we do have some shallow convection offshore moving west into this region. Thus can not rule out some persistence of this activity into the evening hours. Given this threat, and the favorable ingredients mentioned above, a conditional flash flood risk likely exists. Observational trends will need to be monitored closely over the next few hours, as any continued persistence of slow moving heavy convection would result in an increased urban flash flood risk. Chenard ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7kk799mlQvnGdByWQCkXALSu5aeDB3Vuq6UmuoL7tSLMTE_U6oAGAunxRlSefSzJ4yJP= rjzt9fmdfk-I-r8dJZVtQQQ$ for graphic product... ATTN...WFO...MFL... ATTN...RFC...SERFC...NWC... LAT...LON 26548022 26498003 26337995 26117997 25928003=20 25818011 25738022 25748045 25778051 25908056=20 26178053 26298049 26438041=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) .