Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 29 2023 17:02:48 AWUS01 KWNH 291702 FFGMPD TNZ000-KYZ000-INZ000-ILZ000-MOZ000-IAZ000-292300- Mesoscale Precipitation Discussion 0602 NWS Weather Prediction Center College Park MD 101 PM EDT Thu Jun 29 2023 Areas affected...Illinois, Indiana, Kentucky, northern Tennessee Concerning...Heavy rainfall...Flash flooding possible Valid 291700Z - 292300Z Summary...Clusters of showers and thunderstorms, including an MCS, will move east-southeast through the aftn with rain rates in excess of 2"/hr. Where these storms train, 2-3 inches of rainfall is possible with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this aftn indicates two distinct MCS moving around the periphery of a ridge of high pressure centered over the ArkLaTex. One MCS is dropping through KY while a second one races eastward over IA. Both of these features are remaining strong due to extreme thermodynamics characterized by PWs of 1.7 to 1.9 inches, and MUCAPE analyzed by the SPC RAP of 3000-5000 J/kg. A warm front was analyzed just southwest of these features, with the elevated 850mb front serving as a boundary for continued ascent as SW flow upglides atop it, resupplying these thermodynamics into the region. The lead MCS has already produced locally more than 5 inches according to mesonets, and redevelopment already occurring upstream along an outflow boundary further indicates the strength and potential of this environment. The high-res guidance continues to struggle handling the ongoing evolution, so confidence in their output is suspect. However, the ingredients suggest convection may continue to blossom between the two MCS, before the second feature sweeps through this aftn. Advection of the robust thermodynamics will persist, and may amplify immediately downstream of the trailing MCS as the associated MCV helps to locally back low-level flow. This will drive additional convective development ahead of this MCS, while also allowing the MCS to maintain intensity as it moves east. The backing of the low-level flow, strengthening instability gradient, and orientation of the 500mb heights suggest this MCS should turn southeast, but confidence is low in exactly when this will occur. With rainfall rates of 2+"/hr likely producing more than 1"/15min according to the HRRR, this could quickly result in runoff and flash flooding despite fast forward motion on 25kt Corfidi vectors. Much of this region has been dry until today noted by generally below normal streamflow anomalies and 7-day rainfall. The exception is where heavy rain has occurred already today. FFG exceedance probabilities from the HREF are modest overall, but aligned mean winds/Corfidi vectors and these intense rates indicate some areas could receive an additional 3+" of rain through training/backbuilding. This would likely result in flash flooding if it occurs atop the already hit areas from earlier today in SW IN and W KY, with flash flooding possible elsewhere. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9Qr4m5cRFDQvYZElRbtYAsYSqQFTZ_dLQX2zAsWvCSegQ3kF7NQJCz_BrUPKm2bT8mvJ= Qp6938oj0qPg0DNcz-0vaxM$ for graphic product... ATTN...WFO...DVN...ILN...ILX...IND...LMK...LOT...LSX...MEG... OHX...PAH... ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC... LAT...LON 40868923 40258697 39428572 38128492 37388522=20 36728583 36268646 36138711 36168789 36458881=20 36978932 37948986 38949059 39069068 39839131=20 40739141=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) .