Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jul 27 2025 16:37:18 AWUS01 KWNH 271637 FFGMPD PAZ000-WVZ000-OHZ000-KYZ000-INZ000-272235- Mesoscale Precipitation Discussion 0811 NWS Weather Prediction Center College Park MD 1236 PM EDT Sun Jul 27 2025 Areas affected...Parts of the Ohio Valley Concerning...Heavy rainfall...Flash flooding possible Valid 271635Z - 272235Z SUMMARY...Scattered thunderstorms moving across the Ohio Valley this afternoon will be capable of containing intense rainfall rates within a very moist environment. Isolated rainfall totals up to 3 to 4 inches are possible and could lead to scattered instances of flash flooding, particularly across already saturated soils. DISCUSSION...12Z sounding out of ILN showed a PW of 2.07", which is just under the daily max and well above the 90th climatological percentile. Additionally, the freezing level was reported above 15k feet and well above the daily max. This very moist atmosphere is prominent across the Ohio Valley as westerly flow remains on the northern periphery of a large southeast U.S. upper ridge. This upper ridge continues to direct moisture from the western Gulf, while at the same time an upper shortwave crossing the Lower Great Lakes and Northeast is acting to squeeze this axis of moisture across the Ohio Valley over a more confined corridor. Given this environment, it's expected that most developing showers and thunderstorms be efficient rainfall producers and contain warm rain processes. Satellite and radar depict scattered showers and thunderstorms developing midday, with a more confined axis of thunderstorms located from west-central IN into central OH closer to a surface trough/low-level convergence. Instability continues to increase and SBCAPE was estimated to be at 3500-4000 J/kg per SPC's mesoanalysis. As scattered thunderstorms become more widespread this afternoon and tap into the increasing instability, the available column moisture should allow for rainfall rates to exceed 1-2"/hr and may approach 3"/hr briefly times. Largely westerly flow should keep storms moving, with a slight northerly component to storm motions on the eastern side of this highlighted area in WV. However, some repeating of thunderstorms are possible should they orient in a west-northwesterly direction. Additionally, cell mergers and unpredictability associated with developing outflow boundaries may cause slower storm motions and maximize the available atmospheric moisture content. The 12z HREF neighborhood probabilities for exceeding 3" by 21Z are generally 15-30% and have 30-40% probabilities for exceeding the local 3-hr FFG. The 3-hr FFG is under 2" for a lot of central IN and central OH, with values under 3" elsewhere. Given the potential for intense rainfall rates and somewhat sensitive terrain to overlap, aided by 0-40 cm soil moisture percentiles above 90% from NASA SPoRT, scattered instances of flash flooding are possible through much of the afternoon. Snell ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-aVvruvpykO7NAMQ0G3ha7glhruSYd2K0g_9WldV0wFqPSsUtvY-l6pmWjPt3I196SDt= AmJH1v80hs-FjcMXruorTB4$ for graphic product... ATTN...WFO...CLE...ILN...IND...IWX...JKL...PBZ...RLX... ATTN...RFC...TIR...NWC... LAT...LON 40968495 40498314 40168154 39737965 38887983=20 38288101 38258263 38608423 39078521 39738597=20 40458625 40908587=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .