Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 02 2023 11:50:18 AWUS01 KWNH 021150 FFGMPD KYZ000-ILZ000-MOZ000-IAZ000-KSZ000-NEZ000-021700- Mesoscale Precipitation Discussion 0835 NWS Weather Prediction Center College Park MD 749 AM EDT Wed Aug 02 2023 Areas affected...Portions of the Mid-Mississippi Valley Concerning...Heavy rainfall...Flash flooding likely Valid 021200Z - 021700Z Summary...An impressive MCS will persist this morning before gradually decaying into the early afternoon. Rainfall rates of 2"/hr will train along this MCS, producing an additional 2-4" of rain with locally higher amounts possible. Flash flooding is likely. Discussion...A linear MCS draped from eastern NE through southeast MO continues this morning as noted on the regional radar mosaic. This MCS is continuing to strengthen along its upwind side noted by cooling cloud tops in the GOES-E IR imagery reaching below -70C. This convection is being fueled by weak height falls downstream of a shortwave moving across NE/IA, traversing the periphery of a mid-level ridge to the south. An impressive 850mb LLJ of 35-45kts measured via regional VWPs is locally backing in response, to surge northward intense moisture flux of +2 to +2.5 sigma according to the SREF. The accompanying WAA is helping to drive additional convective development as thermodynamic advection occurs beneath 2000-3000 J/kg of MUCAPE and PWs of 1.9-2.1 inches. This event has already resulted in MRMS measured rainfall of 6-8" in some areas overnight, and rainfall rates are still 2-2.5"/hr in deeper convection as estimated by KLSX WSR-88D. The LLJ which is responsible for most of this activity is likely to begin to veer to the east and weaken in the next few hours. However, the upstream shortwave and downstream thickness diffluence should allow the intensity to maintain through the late morning. While there is some uncertainty into the placement of the axis of heaviest rainfall, HREF EAS probabilities for more than 1" in the next 6 hours are quite high along the nose of this LLJ where moisture transport vector convergence is maximized. As the LLJ veers, Corfidi vectors are likely to respond by backing more to the SW and weakening, suggesting continued backbuilding, with training from the NW to SE along the MCS also expected. With rain rates progged by the HREF to exceed 2"/hr at times, this could result in an axis of 2-4" of rain, with locally higher amounts possible as reflected by some low end HREF probabilities for 5". This region has already experienced a corridor of of 2-5" of rain with local amounts above 6" overnight. This has primed the soils and compromised FFG to as low as 0.75"/1hr which will likely be exceeded in the most intense cores as the HRRR shows locally up to 1"/15 minutes. As the LLJ veers the entire system should begin to weaken and push a bit farther east before decaying, but for the next several hours flash flooding is likely, especially where heavy rain returns atop already saturated soils. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!54hn7JV-UNIfBGeLbk6n-O50ZL42jnk0r5MHs9ImFp6lhzLjELg5SL04Co9DDTnMO5aO= yC__a74mA5GVZASszCwUVU8$ for graphic product... ATTN...WFO...DMX...DVN...EAX...FSD...GID...ILX...LSX...OAX... PAH...SGF...TOP... ATTN...RFC...LMRFC...MBRFC...NCRFC...NWC... LAT...LON 42269642 42079409 41249183 39869037 38378952=20 37478924 36898920 36588936 36768987 36899012=20 37589136 38819338 39369528 40269714 41389783=20 41979762=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) .