Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Aug 01 2023 11:54:29 AWUS01 KWNH 011154 FFGMPD MOZ000-011700- Mesoscale Precipitation Discussion 0825 NWS Weather Prediction Center College Park MD 754 AM EDT Tue Aug 01 2023 Areas affected...Missouri Concerning...Heavy rainfall...Flash flooding likely Valid 011153Z - 011700Z Summary...Showers and thunderstorms will continue to train to the southeast this morning with rain rates of 1-2"/hr. This will produce additional rainfall of 2-4" in some areas, falling atop pre-saturated soils. Flash flooding is likely. Discussion...The GOES-E IR imagery this morning shows a persistent MCS over central Missouri with continued cloud top cooling occurring on the upwind side of this system. Recent cloud top temperatures have fallen below -70C, indicative of still strengthening updrafts across the area. Synoptic level ascent is modest overall driven by a weak impulse rotating within NW flow around the periphery of an expansive mid-level ridge to the south. However a slow veering of the 30-40 kt LLJ noted in regional VWPs is surging moisture flux above +3 sigma according to the SREF into the Central Plains/MS VLY, and converging efficiently along the nose of this jet noted by a collapse of moisture transport vector length. This ascent is occurring within favorable thermodynamics characterized by PWs of 1.8-2.0 inches, and MUCAPE of around 2000 J/kg, which has resulted in a narrow axis of 1-4" of rain overnight, with local amounts to 6" noted in mesonets. The recent HRRR and ARW runs are handling the current radar pretty well this morning, and are relied upon most heavily for the evolution. As the LLJ continues to veer to become westerly, it should result in a slow weakening of the MCS. The speed at which this occurs though is probably going to be slower than guidance suggests due to continued thermodynamic advection and modest thickness diffluence to support intensity of convection. The HREF suggests rainfall rates will persist at 1-2"/hr for several more hours, and with the mean 0-6km wind aligned to the nose of the LLJ, training of cells is likely. Additionally, there may be some backbuilding of echoes both to the NW and W, into the greater instability, which will lengthen the duration of heavy rain. Where the most intense cells can train most efficiently, 2-4" of rain is possible as reflected by HREF exceedance probabilities for 3+" reaching 30-40%. By late morning/early aftn this MCS should wane more rapidly as it begins to advect more strongly to the east and into weaker thermodynamics. Rainfall overnight has saturated the soils noted by HRRR 1cm soil moisture of 100% in some areas. FFG is as low as 1.5-2"/1hr for which the HREF has a 20% chance of exceedance, although FFG is likely lower than that in many areas due to the overnight rain. While some uncertainty exists in the evolution this morning, it is likely anywhere training can occur of these rain rates, flash flooding will occur, but will be most likely should training occur atop the most vulnerable soils where any additional rainfall will rapidly become runoff. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-lt4RGbaXRmVLoiwjdC952oIrPRdz7VQVxJReyxLz_TKPjTegEuMCNwSajZg0upwZHer= 9KQczjxMHLJ6RjWxRVlmCHY$ for graphic product... ATTN...WFO...EAX...LSX...SGF... ATTN...RFC...LMRFC...MBRFC...NCRFC...NWC... LAT...LON 40309371 39979256 39109156 37979115 37239119=20 36929160 37229244 37729310 38329370 38869405=20 39299421 39959419=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) .