Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 18 2023 03:38:17 AWUS01 KWNH 180338 FFGMPD KYZ000-INZ000-180800- Mesoscale Precipitation Discussion 0755 NWS Weather Prediction Center College Park MD 1137 PM EDT Mon Jul 17 2023 Areas affected...southern IN and northern KY Concerning...Heavy rainfall...Flash flooding possible Valid 180335Z - 180800Z Summary...1-2"/hr rainfall rates with localized training to persist in the near-term, possibly resulting in totals of 2-4". Isolated flash flooding is possible. Discussion...Convection is backbuilding late this evening across southern IN, just ahead of a quasi-stationary surface front to the west to northwest. The mesoscale environment is characterized by an instability gradient of 500-2500 J/kg (with lower values towards the NE as a result of the cold pool), precipitable water values of 1.4-1.6 inches (between the 75th and 90th percentile, per ILN sounding climatology), and effective bulk shear of 25-35 kts. With the mean wind and upwind propagation vectors parallel to the orientation of convection, additional backbuilding is anticipated along the western flank of the complex, where MRMS has indicated 1.5-2.5"/hr rates having already occurred over the past couple of hours. These rates are likely a bit overdone due to hail contamination, as the multi-sensor pass of MRMS lowers the rates closer to 1-2"/hr (largely due to rain gauge incorporation around the Bloomington metro area). Flash Flood Guidance is relatively high locally just south of Bloomington (2.5-3.0" over 3-hr), but this western flank is likely to continue propagating ESE into the IN/KY border region where FFGs are lower (as low as 1.0-2.0" over 3-hr around and north of Louisville). With increasing convective inhibition into the night, the longevity of this western flank of storms is rather uncertain (though available instability and shear are certainly supportive). The CAMs have generally underdone the intensity of the ongoing storms, and the HRRR in particular has been quick to kill convection off (even after correctly assimilating much of it). It seems reasonable that these 1-2"/hr rates may persist for at least a few more hours along the western flank, and this could result in localized short-term totals of 2-4" into portions of southern IN into northern KY. Isolated flash flooding is considered possible. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!__2lvmbXaa_PA5N0MK3hR0BdUBYtC9yavP0QW_7a5VdzILXS-ddjn6bVLZRV2Yelz5D2= 3C_Xrk0zR2DY4MIUZngMXJw$ for graphic product... ATTN...WFO...ILN...IND...LMK... ATTN...RFC...OHRFC...NWC... LAT...LON 39308651 39188581 38958500 38758446 38448411=20 37858442 37858572 38608720 39078749 39288710=20 =20=20=20=20=20=20=20=20=20=20=20=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) .