Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 08 2025 20:16:27 AWUS01 KWNH 082015 FFGMPD ILZ000-MOZ000-090200- Mesoscale Precipitation Discussion 0622...Corrected NWS Weather Prediction Center College Park MD 415 PM EDT Tue Jul 08 2025 Corrected for Graphic Areas affected...Southern Missouri through Central Illinois Concerning...Heavy rainfall...Flash flooding likely Valid 082009Z - 090200Z Summary...Showers and thunderstorms will steadly expand across Missouri and Illinois into the evening. Rainfall rates of 1-2"/hr are likely, which through training could produce 2-4" of rain with locally higher amounts. This will likely cause flash flooding. Discussion...The GOES-E IR imagery this afternoon shows rapid cloud-top cooling associated with a line of deepening convection from central Illinois through southwest Missouri, including the St. Louis vicinity. These thunderstorms are rapidly intensifying within an impressive overlap of ascent and thermodynamics. A shortwave is noted in WV imagery moving over central MO, while a surface wave and accompanying trough continue to dig southeast. Additionally, a belt of enhanced westerlies is noted at 300mb tracking overhead, providing additional, and locally enhanced, lift. This deep layer ascent is acting upon favorable thermodynamics with PWs above 1.75 inches and MLCAPE over 2000 J/kg. A pronounced CAPE gradient exists from NW to SE along this surface trough, providing the focus for thunderstorms, within which radar-estimated rain rates have already surpassed 2"/hr. Confidence is increasing that the flash flood risk will rapidly increase during the next few hours. As the surface trough drops slowly southeast and the accompanying wave of low pressure skirts into IL, it will interact with even more robust thermodynamics. This will be due to generally modest 850mb inflow from the SW at 10-15 kts impinging and converging into the low-level convergent boundary/instability gradient. At the same time, the narrow corridor of enhanced westerlies will maintain generally westerly 0-6km mean winds to align to the surface boundary, while concurrently enhancing bulk shear to force better, although still modest, storm organization. At the same time, Corfidi vectors will remain parallel to the mean flow and surface trough, indicating a high likelihood of training as storms back build into the greater instability and then track along the boundary. Rain rates in excess of 1"/hr are likely (>70% chance), with 2+"/hr possible (40% chance) as warm rain processes dominate thanks to warm cloud depths approaching 13,000 ft. While the most pronounced training may occur across MO, there is an enhanced rainfall risk into central IL as well as the surface wave moves into the area and provides a focus for some slow moving/regenerating cells. With these intense rain rates expected to continue, this could produce 2-4" of rain, with locally higher amounts above 5" forecast by 10-20% chance of exceedance on the HREF. The CAMs are in very good agreement with this evolution the next few hours as reflected by significant (20-40%) 1"/6hrs HREF EAS probabilities that include St. Louis, MO and Springfield, IL. The limiting factor to flash flood instances may be antecedent dryness and FFG that is generally 2-3"/3hrs. However, both the HREF and REFS indicate a 30-40% chance of exceedance, and the urban areas are even more vulnerable, so instances of flash flooding are likely as cells train through the evening. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6-c-V9g61S8pWuciJPkWcCV0uuHqMbUY8dyFBgJgY7LIldR_fdZUVUszydZ9DpOscenk= f2pOe2qgHJrsbyAI1uf48ks$ for graphic product... ATTN...WFO...EAX...ILX...LOT...LSX...SGF... ATTN...RFC...KRF...MSR...ORN...TIR...TUA...NWC... LAT...LON 41148872 40728810 39968796 39208838 38448945=20 37729087 37379241 37279334 37289406 37499450=20 37849435 38229327 39119198 40009049 40898930=20 =20=20=20=20=20=20=20=20=20=20=20=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .