Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 18 2025 23:16:58 AWUS01 KWNH 182316 FFGMPD WVZ000-OHZ000-TNZ000-KYZ000-INZ000-190430- Mesoscale Precipitation Discussion 0480 NWS Weather Prediction Center College Park MD 716 PM EDT Wed Jun 18 2025 Areas affected...Southern OH...Central KY...Middle TN... Concerning...Heavy rainfall...Flash flooding possible Valid 182315Z - 190430Z SUMMARY...Increasing convective coverage capable of locally exceeding lower than normal hourly FFG due to well above normal soil saturation. Hourly 1-2" totals and some possible short-term storm scale interactions may allow for some isolated totals over 2-3", resulting in widely scattered low-end incidents of flash flooding through early overnight period. DISCUSSION...RADAR mosaic depicts a mature, strong but very progressive squall line crossing eastern IND into OH. This line has been fairly consistent in producing .5-1.25" totals along its path through IND; however, this has not intersected areas of recent saturation until moving into southwest/southern Ohio.=20 Here, 0-40cm relative soil saturation ratios are at or above 60% which is well into the 90th to 99th percentile per NASA SPoRT LIS products and this is more so south across much of KY into western and Middle TN.=20 However, stronger surface to boundary layer convergence was slightly weaker and could not break the cap across much of the pre-frontal pressure trof/convergence boundary. Air remains very unstable with MLCAPE of 2500-3000 J/kg from Cincinnati across into Western TN. Ample moisture in the low to mid 70s (Tds) and total PWats of 1.75 to 1.9", suggest any thunderstorms to develop will have capability of producing 1.5-2"/hr rates. VWP and RAP analysis suggest as the MCV is lifting further north the winds had not been strong enough or have sufficient directional convergence; but recent trends suggest a slight increase in both wind speed as the LLJ diurnally strengthens and a slight increase of about 10-15 degrees from 925-850mb has seen a steady southwestward expansion of the deep moisture convergence axis into western and middle TN.=20 As such, individual cells have broken the cap through much of the line and continue to expand as they progress eastward.=20 Further north into OH, stronger convergence/mature updrafts have been been outdone by forward speeds to result in hourly FFG exceedance, though as they reduce below 1.5" and forward progression reduces slightly further from the lifting shortwave/forcing increased duration suggests scattered incidents of exceedance are possible. Further south, deeper layer steering flow is a bit more west to east and slower by 5-10kts, also supporting increased duration. Stronger upstream LLJ/moisture convergence may also support flanking development within the storm scale environment to further increase overall duration. Similarly though, hourly rates of 1.5-2" are likely along the line with sub-hourly totals expected to be at or slightly above scattered along the line. As such, low-end flash flooding incidents are becoming increasingly possible through the late evening/early overnight period. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7OFUDBMGYjpw1V5tOuJZB-o5oYR3qQA9T73TnoqN69omVoVQ73dbVrDktZFeHaHUH4_t= dUfr4JMRYa4WRTZ_zJtw2WA$ for graphic product... ATTN...WFO...ILN...JKL...LMK...MEG...OHX...PAH...RLX... ATTN...RFC...ORN...TIR...NWC... LAT...LON 39948284 39728209 39078151 38158205 37428310=20 36678472 35418817 36328892 37788688 38748549=20 39238484 39838404=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .