Flash Flood Guidance
Issued by NWS
Issued by NWS
111 AWUS01 KWNH 240326 FFGMPD KYZ000-INZ000-ILZ000-MOZ000-240924- Mesoscale Precipitation Discussion 1046 NWS Weather Prediction Center College Park MD 1125 PM EDT Mon Sep 23 2024 Areas affected...southern Illinois, southern Indiana, northern Kentucky Concerning...Heavy rainfall...Flash flooding possible Valid 240324Z - 240924Z Summary...A cluster of thunderstorms was intensifying over southwestern Illinois and will move eastward across the discussion area over the next 6 hours. Isolated instances of flash flooding are possible with this activity. Discussion...Recent radar/satellite imagery depicts expanding convective coverage along an axis extending from near Mount Vernon, IL southwestward through Cape Girardeau, MO. These storms were loosely organized, with a number of cell mergers across south-central Illinois and a limited amount of training closer to Cape Girardeau. The storms were being forced by 1) a strong mid-level wave just east of St. Louis and 2) sufficient moisture/instability (~1000 J/kg MLCAPE and 1.7 inch PW values) for strong updrafts and efficient rainfall. Recent MRMS imagery depicts a gradual increase in coverage of 1-1.5 inch/hr rainfall rates that were beginning to approach one-hour FFG thresholds across southern Illinois. Models/objective guidance suggests that these trends will continue with eastward extent toward southern Indiana and northern Kentucky over the next 3-6 hours. Storms should reach southwestern Indiana and vicinity around 0530Z. The loosely organized nature of the storms (with occasional development but downstream and southwest of the majority of ongoing convection) should continue to allow for occasional cell mergers/training and spots of 1-2 inch/hr rain rates at times. These rates should fall on ground conditions characterized by 1.5-2.5 inch/hr FFG thresholds, and the spotty nature of the heavier rain rates suggest isolated flash flood potential especially in low spots and urbanized areas. Cook ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...ILN...ILX...IND...LMK...LSX...PAH... ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC... LAT...LON 39438581 39148495 38508490 37678540 37188737 37198911 37748959 38648932 39208835