Flash Flood Guidance
Issued by NWS
Issued by NWS
621 AWUS01 KWNH 192229 FFGMPD WIZ000-MNZ000-IAZ000-200428- Mesoscale Precipitation Discussion 1034 NWS Weather Prediction Center College Park MD 628 PM EDT Thu Sep 19 2024 Areas affected...portions of southern/central Minnesota and Wisconsin Concerning...Heavy rainfall...Flash flooding possible Valid 192228Z - 200428Z Summary...Isolated/localized flash flood potential exists through the early afternoon as a complex of thunderstorms produce heavy rainfall across the discussion area. Discussion...Over the past 1-2 hours, progressive convection has increased in coverage and evolved into a more organized/focused area of cells and linear segments generally extending from near LaCrosse to Owatonna (along I-90/US 14). These storms were in a moist, unstable warm sector, with 1.5 inch PW values and ~2000 J/kg MLCAPE values supporting robust updrafts and spots of 1 inch/hr rain rates. The storms were embedded in fairly strong flow aloft (resulting in 40-kt storm motions), but were oriented favorably for training especially along the aforementioned I-90/US 14 corridor. As cells continue to mature in this corridor (while migrating east-northeastward into Wisconsin), the expectation is that a few areas of rain rates approaching 2 inches/hr could materialize and cause isolated/localized flash flood issues through at least 03Z tonight. The complex will produce these rain rates atop areas of ground conditions that exhibit slightly more sensitivity with northeastward extent. Soils are more moist in central Wisconsin, and FFGs are slightly lower there (1.5 inch/hr thresholds) compared to the remainder of the discussion area (closer to 2 inches/hr). The overall threat of flash flooding is a bit conditional on heavier rain rates materializing on sensitive soils. This threat should persist through the 03-04Z timeframe. Cook ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...ARX...DLH...GRB...MKX...MPX... ATTN...RFC...NCRFC...NWC... LAT...LON 45619071 45328955 44448918 43868942 43489096 43559310 43909375 45119316 45459238