Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 31 2024 17:08:32 AWUS01 KWNH 311708 FFGMPD ILZ000-MOZ000-IAZ000-312100- Mesoscale Precipitation Discussion 0767 NWS Weather Prediction Center College Park MD 107 PM EDT Wed Jul 31 2024 Areas affected...southeast Iowa, northeast Missouri, central Illinois Concerning...Heavy rainfall...Flash flooding possible Valid 311706Z - 312100Z Summary...An MCS ongoing this afternoon will continue to drive training convection from NW to SE with rainfall rates of 2"/hr. This could produce an axis of 2-3" of additional rainfall with locally higher amounts. Flash flooding is possible. Discussion...Persistent MCS noted on the regional radar mosaic is continuing to drive training of cells with heavy rain rates across southern IA and into western IL. Although the primary MCV has shifted east well away from the area, the lingering convergent boundary to its W/SW continues to be an impetus convective development. This is due in part to 15-20 kts SW 850mb winds driving WAA into the region, with persistent thermodynamic advection of elevated PWs and CAPE accompanying this flow. This is also lifting isentropically above a stationary front analyzed by WPC over Missouri, and converging efficiently into axis of convection. Extremely steep lapse rates between 850-500mb, an EML, was measured on the 12Z U/A soundings out of LBF and OAX, which is also being advected downstream to allow convection to continuously regnerate. Rainfall rates of 1-2"+/hr have resulted in a narrow corridor of 1-4+" of rain this morning, and flash flood warnings are currently in effect. The high-res CAMs are really struggling with the activity today, and in reality none of them models are analyzing the current activity correctly. This causes lower than typical confidence in the evolution, but the ingredients and observations suggest the flash flood threat will persist for a few more hours. 850mb winds are progged to remain out of the SW, which will continue to originate from a plume of 8C/km mid-level lapse rates to resupply impressive thermodynamics northward. With little change in the environment, mean 0-6km winds and nearly aligned propagation vectors to this convergent axis suggests storms will repeatedly develop along the outflow boundary and then advect southeast. Rain rates should continue at 1-2"/hr, which through training could produce an additional 2-3" of rainfall. One concern about the next several hours is the outflow boundary which has appeared on the GOES-E visible imagery recently, and is beginning to shift southeast a bit faster to outrun the convection. While this boundary could serve as a continued focus for convergent ascent, if it outraces the most intense instability gradient or moves farther south into less saturated antecedent soils, it could cause a wane in the flash flood risk. While it is probable this will slowly occur in the next few hours, until that time, any training of these intense rates across sensitive soils could cause additional flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Iedc3BnZxtEjlKZDIeWAI0u4JkV9beIBTf2oG2ZxX7iv9gc2qVt0L7vUmlaUR4LuhBn= Q8qvOG9XAXlN7HyiiWM91nc$ for graphic product... ATTN...WFO...DMX...DVN...EAX...ILX...LSX... ATTN...RFC...MBRFC...NCRFC...OHRFC...NWC... LAT...LON 41359202 40848982 39558799 39028805 38718916=20 39149129 39789289 40509363 41109364=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) .