Flash Flood Guidance
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Issued by NWS
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598 AWUS01 KWNH 260350 FFGMPD TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-260900- Mesoscale Precipitation Discussion 0499 NWS Weather Prediction Center College Park MD 1145 PM EDT Tue Jun 25 2024 Areas affected...Southeaset MO...Southern IL...Southwest IND...Western KY...Far Northwest TN... Concerning...Heavy rainfall...Flash flooding possible Valid 260345Z - 260900Z SUMMARY...Slow moving convection with capability of 1.5-2"/hr and spots of 2-4" as it slides eastward pose possible flash flooding. DISCUSSION...GOES-E 10.3um and Regional RADAR mosaic depict a cluster of cooling thunderstorms near the confluence of the Ohio and Mississippi River. The weak MCV across S IL is starting to slide eastward into the western edge of the larger scale positive tilt trough across the Ohio Valley. This has reduced forward progression to the south, though meso-high/cold-pool across SE MO is sharpening the moisture convergence along the western upstream edge to bring back some increased vigor to the cells over the last hour or so. Cell mergers are resulting in spots of 2"/hr+ before reducing to a more average 1.5"/hr along the length of the line. While the area is stabilizing slightly and the outflow boundary is starting to push, the overall environment will remain weakly supportive of convection with southerly flow continuing to support some moisture flux up the MS and TN Valleys with 2500-4000 J/kg of available weakly capped MUCAPE. 850-700mb layer is starting to veer and become more west to east, parallel to the convective bow and supporting 15-20kts of steering to allow for training profile, while having 20-25kts of LLJ entering the upstream edge for some favorable back-building. This should support a few hours of west to east training. To make matters even further favorable, the complex is moving into a divergent 500-1000 thickness pattern reducing propagation vectors to 0-5kts through W KY, and as the cold pool weakens...southward propagation should diminish. While training and limited southerly inflow at cloud base and stabilizing lower atmosphere likely will reduce convective coverage with time...spots of 2-4" are still possible through the middle of the night, next 3-4 hours. While the area, has been relatively dry; there is a narrow axis of average to slightly above average soil saturation across SE MO into W KY where relative soil moisture ratios are above 50%, and therefore FFG values are within reach locally with 3hr values of 2-3" to be potentially exceeded over the next 3-5hrs. As such, flash flooding is considered possible through 09z, slowly expanding eastward into SW IND. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...LMK...LSX...MEG...OHX...PAH... ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC... LAT...LON 38378761 38178643 37198667 36678723 36248817 36078901 36149010 36679102 37069089 37399058 38148905