Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 09 2025 08:52:58 AWUS01 KWNH 090852 FFGMPD WIZ000-MNZ000-IAZ000-091435- Mesoscale Precipitation Discussion 0884 NWS Weather Prediction Center College Park MD 452 AM EDT Sat Aug 09 2025 Areas affected...northern IA into southeastern MN and western WI Concerning...Heavy rainfall...Flash flooding likely Valid 090851Z - 091435Z SUMMARY...The threat for flash flooding is expected to increase this morning from northern IA into southeastern MN and western WI. Areas of training with rainfall rates in the 1-3 in/hr range are expected with 2 to 4+ inch totals through 14Z. DISCUSSION...Regional radar imagery at 0830Z showed an expanding cluster of thunderstorms just west of Minneapolis with outflow oriented ENE to WSW moving into the downtown portion of the city. This cluster has produced rainfall rates of 0.5 to 1.5 inches in 15-30 minutes from training over Wright County and a short term flash flood threat appears likely into the Twin Cities over the next hour or so. Elsewhere across MN and IA, thunderstorm activity was fairly limited in coverage but was beginning to trend upward ahead of a large closed low over the Saskatchewan/U.S. border, steadily advancing eastward with downstream ascent over the eastern Dakotas into MN. At the surface, a slow moving (nearly stationary) front was analyzed over west-central MN, from north to south, with a secondary cold frontal surge with notable dewpoint falls to its west across the Red River Valley. Ascent ahead of the large mid to upper-level low, including upper level divergence and diffluence tied to the right-entrance region of a 100 kt jet over ND, will act to further increase thunderstorm coverage over the next 3-6 hours over the region. As the ongoing cluster of thunderstorms to the west of MSP continues to shift eastward into northwestern WI over the next couple of hours, expansion of a second thunderstorm cluster is expected from northwestern IA into southeastern MN ahead of the cold front within a zone of low level moisture transport fed by 30-40 kt southerly 850 mb winds. This area of thunderstorms is expected to follow the deeper layer mean flow toward the northeast. As the secondary cold front reaches northwestern IA near/just after 12Z, another round of thunderstorms is expected to develop over northwestern IA with similar northeastward advancement. The pattern will favor repeating rounds of thunderstorms with embedded periods of training which are likely to generate some areas of flash flooding with rainfall rates of 1-2 in/hr, perhaps as high as 2-3 in/hr within the anomalously moist/unstable airmass. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6g9HpouFQjdOui-ds94a79wlXIembMAjSiYu1hcWO2YvhV7RdE11DohMr9C4_akR4YJo= oBn5VaZbPvyvcQBKjoEMdpQ$ for graphic product... ATTN...WFO...ARX...DLH...DMX...FSD...GRB...MKX...MPX... ATTN...RFC...KRF...MSR...NWC... LAT...LON 46119202 45699032 44538980 43709015 42849193=20 42089495 42709620 43599584 45149406=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) .