Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 23 2025 21:04:59 AWUS01 KWNH 232104 FFGMPD MIZ000-WIZ000-MNZ000-240200- Mesoscale Precipitation Discussion 0785 NWS Weather Prediction Center College Park MD 503 PM EDT Wed Jul 23 2025 Areas affected...Southeast Minnesota, Central into Northern Wisconsin Concerning...Heavy rainfall...Flash flooding possible Valid 232101Z - 240200Z Summary...Showers and thunderstorms will gradually expand in coverage and train through this evening. Rainfall rates of 1-3"/hr are expected, which through this training could produce 2-3" of rain with locally higher amounts. This may lead to flash flooding. Discussion...The regional radar mosaic this afternoon shows increasing thunderstorm activity within multiple clusters moving across southeast Minnesota and into Wisconsin. This activity is blossoming along a combination outflow boundary/stationary front analyzed via 20Z observations draped across the region. Into this front, low-level moist flow at 850mb has featured local backing across Iowa, helping to surge thermodynamics northward more orthogonally into the front to enhance convergent ascent. This local backing is due in part to a shortwave noted in GOES-E WV imagery lifting across SW Minnesota, which is helping to draw PWs of 1.8-2.2 inches and extreme SBCAPE of 4000-6000 J/kg northward. This thermodynamic resupply is driving an intensification and expansion of convection (noted via the radar mosaic and the GOES-E day-cloud phase microphysics RGB), with radar-estimated rain rates of 2-3"/hr according to KARX. During the next few hours, the CAMs are in generally good agreement that the front will oscillate subtly north/south in response to convective outflows and the intensifying LLJ, leading to a corridor of focused ascent into the evening. With impressive thermodynamics remaining in place, this will result in multiple rounds of thunderstorms developing across MN and lifting E/NE along the front. While there is some uncertainty as to exactly where the corridor of heaviest rain will occur due to fluctuations in the frontal position, in general, a WSW to ENE oriented swath of heavy rain is likely as 0-6km mean winds of 20-25 kts align parallel to the boundary. This is a clear training signature, and as rain rates pulse at times to 3"/hr, where multiple rounds or backbuilding into the greater thermodynamics can occur, total rainfall of 2-3" is expected, with local amounts up to 5" possible (10-15% chance for 5"). 0-10cm soil moisture from NASA SPoRT is generally normal to slightly above normal (70th-80th percentile) and FFG is modest in response. The HREF probabilities are only 10-15% for FFG exceedance, but latitudinal differences in the HREF members suggests these neighborhood probabilities are likely too low, especially across central WI and far southeast MN where the CAMs are initializing too far north with current activity. Regardless, the intensity of these rain rates combined with the expected training/backbuilding later this afternoon suggests that rapid runoff may occur even atop drier soils, with impacts from flash flooding most likely atop urban areas or where the most pronounced training can occur. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7hSbLtNhPjz4rSwFESPtfe9FrwBOQ4rVBs_QJZBVxSpyG8NjxCxA72MfVNheAGjqV7tf= imjoFGtnrMAPQDhcy_oIzqc$ for graphic product... ATTN...WFO...ARX...DLH...GRB...MPX...MQT... ATTN...RFC...MSR...NWC... LAT...LON 46018936 46008852 45788792 45398752 44888753=20 44478803 44188910 44019013 43849127 43729224=20 43649294 43619344 43839386 44539376 45279308=20 45709226 45909147 45979036=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) .