Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jul 01 2023 11:02:57 AWUS01 KWNH 011102 FFGMPD OHZ000-KYZ000-INZ000-ILZ000-MOZ000-011600- Mesoscale Precipitation Discussion 0611 NWS Weather Prediction Center College Park MD 702 AM EDT Sat Jul 01 2023 Areas affected...Ohio River Valley from Illinois to Ohio Concerning...Heavy rainfall...Flash flooding possible Valid 011101Z - 011600Z Summary...an MCS moving across Illinois will advect eastward through late morning. Rainfall rates in training convection will exceed 2"/hr at times, which could produce 2-3" of rain and isolated instances of flash flooding. Discussion...The regional radar mosaic this morning indicates a large cluster of thunderstorms embedded within an MCS moving eastward across IL and into western IN. This cluster is being driven by a potent shortwave identified on the GOES-E WV imagery ejecting out of Missouri, interacting with a potent 30-40 kt SW LLJ arcing into IN/KY. PWs across the area as measured by GPS are 1.5-1.8 inches, around the 90th percentile for the date, which are combining with SPC RAP analyzed MUCAPE of 1000-2000 J/kg to produce robust thermodynamics favorable for heavy rainfall. Recent rain rate estimates from KVWX WSR-88D have been as high as 2-2.5"/hr, resulting in local mesonet observations above 2 inches and FLASH response as high as 105% QPE:FFG ratio and 200-300 cfs/mi unit streamflow. The high-res guidance is struggling to initialize the ongoing convection, so confidence in evolution is modest. However, the impressive LLJ will likely remain subtly backed for the next few hours downstream of the shortwave, providing favorable warm advection to persist and intensify convection. This is already being noted by re-development within the meso-warm sector along the nose of the LLJ, and with this airmass originating from a region of PWS nearing 2" and MUCAPE approaching 4000 J/kg, it seems likely this cluster will persist for several more hours. The exact track of this MCS is also uncertain as it should turn SE into the better moisture, but 500mb isoheights are generally west-to-east, and the driving shortwave is potent, so this may track farther east than south. However it evolves, the environment will support 2"+/hr rainfall rates, and as Corfidi vectors collapse to just 5-10 kts and veer to become nearly aligned anti-parallel to the mean flow, backbuilding of echoes is likely which could support rainfall approaching 1"/15min in the most intense convection. Parts of this area have been saturated recently, noted by AHPS 7-day rainfall above 300% of normal across KY and southern IN, resulting in lowered FFG to 1.5-2"/3hrs. While HREF exceedance probabilities are low, primarily due to a lack of model agreement, the backbuilding/training of these echoes supports at least an isolated risk for exceeding these thresholds. Where the most impressive training occurs, rapid runoff is expected which could lead to instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5GqFeoH61qlCc-fHvegiMp2arjNtInjyGq3NY3TuSjRamWYBsl0UG4zWtoYMY1VttCrU= zt2HJBbjanbrYImhbHqxdtE$ for graphic product... ATTN...WFO...ILN...ILX...IND...IWX...JKL...LMK...LOT...LSX... PAH...PBZ...RLX... ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC... LAT...LON 40678508 40058220 38988211 38398275 38078394=20 37598659 37568878 37728993 38269076 39389052=20 40198908 40578758=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) .