Flash Flood Guidance
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Issued by NWS
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574 AWUS01 KWNH 242213 FFGMPD ILZ000-MOZ000-ARZ000-250330- Mesoscale Precipitation Discussion 0317 NWS Weather Prediction Center College Park MD 612 PM EDT Fri May 24 2024 Areas affected...Southern MO...Northern AR...Southern IL Concerning...Heavy rainfall...Flash flooding possible Valid 242210Z - 250330Z SUMMARY...Robust thunderstorm activity flaring up along a prefrontal surface trough and an approaching cold front may congeal over parts of the highlighted region this afternoon and evening. Hourly rainfall rates could top 2"/hr and may result in areas of flash flooding. DISCUSSION...Satellite and Doppler Radar depicted healthy and severe-warned cells tracking through the heart of Missouri. These storms are forming along a surface trough that also has ties to the ongoing convection that has caused flash flooding north and St. Louis. Meanwhile, a cold front is also triggering thunderstorms with the cells marching towards southern MO thanks to persistent westerly 850-300mb winds aloft. The environment out ahead of the cold front is quite unstable with RAP mesoanalysis sporting over 3,000 J/kg of MLCAPE in central MO. Meanwhile, PWs are close to 1.5" in southern MO with a steady influx of low-level moisture being directed at the Ozarks and along the surface convergence zone. RAP mesoanalysis depicts as much as 30-40 kts of effective bulk shear within the atmosphere which will help to sustain these storms into the early evening hours. In terms of soundings, the RAP shows warm cloud layers close to 10,000ft deep, but mean cloud layer winds are at 30 knots which should keep storms moving along initially. As the two boundaries collide, and outflows from the initial storms in central MO drift south, this will give storms the opportunity to congeal into an organized cluster of storms. This setup will allow for storms to generate excessive rainfall rates of 1.5-2"/hr as they track across southern MO. These storms could track as far south as the Ozarks of northern AR and across the MS River into southern IL based on probabilistic guidance from the 18Z HREF. Soils in the area are not too saturated or too dry, so that will help to limit the areal extent of potential flash flooding. That said, segments where storms congeal and persist over a given area for 2-3hrs at a time could lead to flash flooding in low lying, poor drainage areas. Mullinax ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...LSX...LZK...PAH...SGF...TSA... ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC... LAT...LON 38499153 38208990 37459000 36769090 36339180 36159330 36389435 37369389 38209273