Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 11 2025 03:47:06 AWUS01 KWNH 110346 FFGMPD INZ000-ILZ000-IAZ000-110930- Mesoscale Precipitation Discussion 0642 NWS Weather Prediction Center College Park MD 1146 PM EDT Thu Jul 10 2025 Areas affected...Northern Illinois...Southeast Iowa...Ext Northwest IND... Concerning...Heavy rainfall...Flash flooding likely Valid 110345Z - 110930Z SUMMARY...Lead shortwave with flanking line development and potential for repeating across areas of Northern IL through the overnight hours. Hourly rates to 2"/hr suggest 3-5" totals are possible, resulting in likely incidents of flash flooding. DISCUSSION...Regional RADAR mosaic depicts a mature MCS with strengthening MCV over N IL with moderate shield precipitation straddling the IL/WI line. A surface wave can be analyzed southwest of RPJ with stationary front across NE IL into northern IND, while the trailing boundary extends across into central IA. GOES-E WV and RAP analysis shows the stronger parent shortwave is located much further north across central WI; though a stronger northern stream wave continues to organize upstream across the Missouri River Valley. As such, the combination is helping to retain strong broad southerly LLJ providing WAA and deep moisture convergence in proximity the surface boundary; winds are 20-25kts at 850mb and remain confluent to the shortwave across WI. As such, solid convergence remains along the upstream flanking line across NW IL with thunderstorms still cooling even as the instability has be diminishing relative to upstream as well.=20 Downstream, even lower CAPE values toward NW IND shows the slow erosion of the convective cells and warming tops.=20 CIRA LPW shows 850-700mb layer has been increasing (though recent uptick is likely due to a particular over-estimate of values since 01-02z) but the pattern shows the flux to maintain near 2.0" total PWat values to maintain rainfall efficiency to the convection.=20 Southwest to west-southwest instability flux will also support back-building potentially across into E IA, though capping is a tad stronger. Still, redevelopment in NW IL with slow east to east-southeast propagation will allow for tracks of repeating and potential for multiple hours of 1.5-2"/hr rates. Localized totals of 3-5" are not out of the realm of possibility especially in proximity to I-80. Given FFG values of 1.5-2"/hr and 3hr generally around 2-3"; a few incidents of flash flooding along the line are considered likely. Of particular concern, is upstream development across NEB into central IA, that may intersect with this area toward pre-dawn and will watch the evolution closely...an upstream MPD will also be issued within the next hour or so. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_y3-33BUqIaHK8xEJuHa3-D-W21F2gMVg6eOjrv7yE-1Jx8VGqxkXeHIhrsOtEpWICoD= M0HDfsaoTn8tHbT0_FDF_E0$ for graphic product... ATTN...WFO...DMX...DVN...ILX...LOT... ATTN...RFC...MSR...NWC... LAT...LON 42428874 42408787 41958730 41478709 40898745=20 40618904 40629034 40789204 41069279 41609294=20 41929244 41899131 41979045 42059000 42168949=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .