Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 24 2023 23:33:18 AWUS01 KWNH 242333 FFGMPD MIZ000-INZ000-WIZ000-ILZ000-250330- Mesoscale Precipitation Discussion 0971 NWS Weather Prediction Center College Park MD 732 PM EDT Thu Aug 24 2023 Areas affected...southeastern Wisconsin, northern/central Illinois, northwestern Indiana Concerning...Heavy rainfall...Flash flooding possible Valid 242330Z - 250330Z Summary...Thunderstorms will continue to increase in coverage through 05Z while moving southward across southern Wisconsin/northern Illinois. Flash flooding is possible - especially where backbuilding and localized training of storms is most pronounced. Discussion...Isolated to scattered thunderstorm activity has developed along and just north of a surface front extending from near Milwaukee east-northeastward to near Saginaw over the past couple hours. Cells across southern Wisconsin (near Racine, WI and just east of Madison, WI) have exhibited localized backbuilding, slower storm motions (5-10 knots) and spots of 1+ inch/hr rain rates despite appreciable westerly flow aloft (~30 knots). The rainfall is also falling across urbanized areas of southeastern Wisconsin, and local FFG thresholds (around 1-1.5 inch/hr) being exceeded beneath the storms at times. Given the ongoing mesoscale environment, the potential for localized/urban flash flooding will continue in the short term. Models/CAMs suggest that the slow southward motion of the storms should allow for movement toward the WI/IL border and perhaps the Chicago Metro area over the next 2-3 hours before reaching areas along an axis from near Peoria to Davenport, IA toward 03Z. A conditional threat for urban flash flooding will exist with this activity, although the extent of the risk will likely depend on the forward speed of the convection and its persistence over urban areas. With time, models suggest that storms will grow upscale and begin to forward propagate more quickly to the south, although current radar trends suggest that this process will take some time to unfold. The greatest flash flood risk should exists in the next 2-3 hours (through 02Z or so) and may wane thereafter pending convective trends (and degree of upscale growth). Cook ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5CyXkXs14xVyos0VfaRljLFxLlPD3mKZqKjw9PG_TbN3RXSflvC2B_eyVK4oiqWbtm_V= X9dFvRwMVDoAim7dp5rQzdI$ for graphic product... ATTN...WFO...DVN...ILX...IND...IWX...LOT...MKX... ATTN...RFC...NCRFC...OHRFC...NWC... LAT...LON 43328916 43138776 41608666 40498691 40068886=20 41458983=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) .