Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 13 2023 21:36:22 AWUS01 KWNH 132136 FFGMPD ILZ000-MOZ000-140030- Mesoscale Precipitation Discussion 0290 NWS Weather Prediction Center College Park MD 535 PM EDT Sat May 13 2023 Areas affected...eastern Missouri, western Illinois Concerning...Heavy rainfall...Flash flooding possible Valid 132130Z - 140030Z Summary...A cluster of deep convection was expanding in coverage over the past hour, with storm motions favoring localized training and perhaps an isolated flash flood threat through 00Z. Discussion...A loosely organized cluster of storms was located just east of Saint Louis, MO (20 west SLO). That cluster was moving east at roughly 15-25 mph. A modest increase in upscale growth/forward propagation was noted with this cluster, and an east-to-west band of convection was beginning to materialize on its upstream flank extending through Belleville into areas of the southwestern suburbs of the Saint Louis Metropolitan Area. This orientation (parallel to steering flow aloft) was allowing for prolonged heavier rainfall and rates eclipsing 1-1.5 inches/hour. Additional, slow-moving cells were also located west of Farmington that were also beginning to produce 1 inch/hr rain rates. Some concern exists that as cells continue to expand in coverage over the next few hours, training and cell mergers could produce enough heavy rainfall for a localized/isolated flash flood threat. The environment supporting the activity contains enough instability (2000 J/kg MLCAPE) and moisture (1.8-1.9 inch PW values) to continue supporting efficient rainfall processes and high rain rates. Meanwhile, FFG thresholds in the 1.5-2.5 inch/hr range could be eclipsed in spots where prolonged, heavier rainfall materializes.=20 Observations and radar both suggest that the convective evolution should feature widespread overturning/low-level stabilization over the next 2-3 hours especially as the ongoing cluster maintains a slow southward component to motion. This should result in a brief flash flood threat that probably diminishes some after 00Z, although convective trends will continue to be monitored for any potential upstream development that could lengthen the flash flood risk beyond that timeframe. Cook ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!73ckfrTY6h91YRCT9pnt4k7dIxAhPJv9bHzhBwoQ1ipW9kxJb20VPkirnZrXuwknZRtc= LWrEZ8J2bkUj_09bJCKOmiI$ for graphic product... ATTN...WFO...ILX...LSX...PAH...SGF... ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC... LAT...LON 39408847 38548810 37888836 37078978 37079097=20 37689139 38529126 38879048 39058967=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) .