Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 26 2025 21:01:01 AWUS01 KWNH 262100 FFGMPD WIZ000-MNZ000-IAZ000-270243- Mesoscale Precipitation Discussion 0521 NWS Weather Prediction Center College Park MD 459 PM EDT Thu Jun 26 2025 Areas affected...Central WI...Northeast IA...Southeast MN Concerning...Heavy rainfall...Flash flooding possible Valid 262058Z - 270243Z SUMMARY...Thunderstorm coverage will increase along and north of a frontal boundary draped over southern WI this afternoon and evening. Repeating rounds of strong thunderstorms both along the frontal boundary and with assistance from approaching storms from the west may cause flash flooding. DISCUSSION...20Z surface analysis shows the location of the west-to-east oriented frontal boundary well, with a more organized complex of storms over southeast MN as a remnant MCV tracks towards central WI. Strong 925-850mb theta-e advection is underway over the Upper Midwest and will slowly inch the stationary front north as a warm front this evening. The influence of this low-level theta-e advection is evident in the increasing MUCAPE field in central WI as RTMA 3-hr trends show as much as 600-1,000 J/kg MUCAPE increases over the past 3-hours alone. The Upper Midwest remains ideally positioned beneath the diffluent right-entrance region of a 250mb jet streak and PWs are steadily rising. By 00Z tonight, the highlighted region is expected to see PWs range between 1.75-2.0", which is generally above the 97.5 climatological percentile per ECMWF ensemble guidance. With MUCAPE along the boundary near 2,000 J/kg, and even areas as far north as Green Bay likely to see up to 500 J/kg of MUCAPE, the stage is set for widespread thunderstorms that could contain up to 2"/hr rainfall rates. Aiding in the efficient rainfall production is the presence of vertical wind shear and helicity. Effective bulk shear values >40 kts and effective SRH values >100 m2/s2 support thunderstorms potentially sustaining mesocyclones, which are very efficient rainfall producers. In addition, low-mid level RH values are averaging close to 90% and warm cloud layers per the 18Z RAP for this evening are pegged to be as deep as 13,000ft. West-Central WI also sports highly saturated soils with NASA SPoRT-LIS 0-40cm soil moisture percentiles well above the 90th percentile. As isentropic ascent and low-level moisture advection increase along and ahead of the approaching surface trough, there is the concern for repeated rounds of thunderstorms in parts of the region. Once the cold front approaches the region between 00-02Z, storm motions over central WI should be more continuous off to the north and east. Until then, however, there is a concern for training storms across portions of central WI, far southeast MN, and far northeast IA. Flash flooding is possible this evening, particularly in areas with sensitive soils and where storms train along and north of the frontal boundary in southern WI. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9PrKLtHq8DOxC7ZqVoyNuSVkYvemtuwUdcwVPlfGhdVUgq7Y8wicvr8DPXOXC1wWkZbY= QRfdjODtG7KwXdqHL0K5LVg$ for graphic product... ATTN...WFO...ARX...GRB...MKX...MPX... ATTN...RFC...MSR...NWC... LAT...LON 45329101 45168840 44458740 43388785 43118856=20 43048972 42779142 43249248 43759278 44959268=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) .