Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 30 2023 00:28:38 AWUS01 KWNH 300028 FFGMPD TNZ000-KYZ000-INZ000-ILZ000-MOZ000-300425- Mesoscale Precipitation Discussion 0816 NWS Weather Prediction Center College Park MD 827 PM EDT Sat Jul 29 2023 Areas affected...Lower OH Valley into Middle TN Concerning...Heavy rainfall...Flash flooding possible Valid 300025Z - 300425Z Summary...An advancing convective arc continues to send out an outflow boundary to generate new convection which then merges in.=20 A front up to the north has been rather efficient with heavy rainfall as of late on its northeast side. Hourly rain totals to 2.5" with local amounts to 4" remain possible. Discussion...The guidance continues to lag the progress of a long-lived convective system which is advancing through western KY and into southern IN. An MCV is apparent in radar imagery behind the thunderstorms in southern IL. Precipitable water values of 1.75-2" remain across the area per GPS data. ML CAPE of 2000-4000 J/kg continue to lie to the south and east of the convective area, with CIN eroding in advance of the system. Effective bulk shear is around 25 kts, just enough to maintain convective organization. The mean 850-400 hPa flow should continue to carry the complex east-southeast to southeast. With the mesoscale guidance continuing to play catch up with progression, hourly model runs like the HRRR and RAP have the upper hand, albeit they're probably too slow as well. Used the pattern of the 22-23z HRRR through 06z but used a four hour horizon as a strategy. So far, the more efficient convection has been along the front where occasional warm advection bands previously set up near St. Louis, and then across southern IL. See no reason why this wouldn't continue across southern IN and portions of KY, but with the pattern down south occasionally broadening ahead of the main arc, and then merging in increasingly hourly and overall rain totals, covered the envelope of the overall system as a precaution. Hourly rain total to 2.5" with local amounts to 4" remain possible, with any flash flood issues expected to remain isolated to perhaps widely scattered. Urban areas would be most sensitive, as the region has been fairly dry this past week (outside of where it rained earlier today). Confidence is lower than average in this scenario as it's unclear how long this convective complex can truly hang on. Roth ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4HVORW-Sz0PqocZQazSRLQEoItWAw3ITNIB2mPgOIo8GT2n3r-LlDZB2TG1PAhufcwE1= n0Je2Wsla55LzxfQJiRQim0$ for graphic product... ATTN...WFO...ILX...IND...JKL...LMK...LSX...MEG...OHX...PAH... ATTN...RFC...LMRFC...OHRFC...NWC... LAT...LON 38818824 38448601 37748466 36418488 35678598=20 35618792 35788904 36178983 36888985 37528847=20 38038846 38518870=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) .