Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Aug 17 2025 03:36:19 AWUS01 KWNH 170334 FFGMPD WIZ000-ILZ000-MNZ000-IAZ000-170900- Mesoscale Precipitation Discussion 0947 NWS Weather Prediction Center College Park MD 1134 PM EDT Sat Aug 16 2025 Areas affected...Southeast MN...Northeast IA...Southern WI...Northern IL... Concerning...Heavy rainfall...Flash flooding likely Valid 170335Z - 170900Z SUMMARY...Warm-advection thunderstorms with potential for training and spots of 2-4" across areas of recent heavy rainfall/saturated soils likely resulting in scattered incidents of flash flooding. DISCUSSION...GOES-E WV suite shows increased anticyclonic curvature in upper-level cirrus pattern indicative of shortwave ridging in the wake of the exiting shortwave across the Lower Peninsula of Michigan. The associated surface front extends through central Lake Michigan across southern WI into the northern row of counties in IA; though the effective boundary due to strong overturning from this evening's convection intersects the front near near KPDC and angles southeastward across NE IL into just north of KDNV. Deep layer moisture remains pooled along the frontal zone with 1.75-2" Total Pwats across N IA/S MN before broadening across S WI into northeast IL. LLJ response is a broad southwesterly 15-20kt flow along the entire front; so best moisture convergence/isentropic ascent is at the intersection remains along the intersection of the old outflow boundary and surface front in NE IA/SW WI/NW IL. Upper-level right entrance to the jet further enhances vertical ascent in proximity to the front, also helping to sharpen the isentropes vertically throughout the night. Efficient rainfall production given strong convergence and unstable air with favorable evacuation aloft, should support 1.5-2"/hr rates within the expanding cores.=20 GOES-E 10.3um shows strong cooling tops below -65C along the orthogonal section of ascent, with upstream redevelopment and increasing TCu noted across SE MN. With flanking development and steering flow from NW to SE, a favorable training environment setup may allow for increased duration and localized 2-4" totals are likely especially from SE MN and SW WI, as potential for further upstream development is likely throughout the overnight period as well, and as such an isolated spot over 5" is not out of the realm of possibility.=20 To compound issues, the area has seen recent heavy rainfall and the upper soil conditions remain relatively saturated with 0-40cm ratios well over 50 with spots near 70% across MN, WI (above 90th percentile) before reducing to below 40% over Chicagoland into NW IND per NASA SPoRT LIS product(though tonight's rain, likely improved those values. As such, infiltation may be a bit more difficult and increased runoff is likely to result in scattered incidents of flash flooding overnight tonight.=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4XD5kfk4Uj5z4YB_V5dUsJJ-ohvachmPL8OrbNcd2VWkaq4KXlEBEZC03tNWaNyt83pI= qJgYtt6d7ZR79bcGiDWcutM$ for graphic product... ATTN...WFO...ARX...DVN...LOT...MKX... ATTN...RFC...MSR...NWC... LAT...LON 44199254 44149159 43789046 43278856 42758764=20 41828746 41288783 41278892 41989046 42729175=20 43359272 43649301 44039293=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) .