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Flash Flood Guidance
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Issued by NWS
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854 AWUS01 KWNH 080135 FFGMPD IAZ000-080600- Mesoscale Precipitation Discussion 0587 NWS Weather Prediction Center College Park MD 935 PM EDT Sun Jul 07 2024 Areas affected...Central Iowa Concerning...Heavy rainfall...Flash flooding possible Valid 080134Z - 080600Z SUMMARY...Flash flooding possible as storms move across portions of Iowa with saturated soils. Rates to 2.5 inches per hour possible. DISCUSSION...A potent positively tilted shortwave in the subtropical jet has provided the forcing for scattered showers and thunderstorms to develop over portions of western Iowa this evening. While decently fast-moving, the storms are moving over much of Iowa that has been hard-hit with heavy rainfall over the past couple weeks. Thus, FFGs across the central part of the state are low enough that while conditions for heavy rainfall are somewhat less than ideal, cell mergers and outflow boundary collisions are locally slowing the motion of the storms as they follow the enhanced forcings. Thus, expect with continued development of the storms east across Iowa, additional instances of flash flooding are possible. PWATs across Iowa are around 1.3 to 1.4 inches with MUCAPE values around 2,000 J/kg. These values will support additional storm development over the next few hours. CAMs guidance suggests the storms forming now over the northwestern part of the state will gradually coalesce into a small MCS, which will then weaken as it gets to the eastern part of the state in a few hours due to rapidly decreasing instability along the Mississippi River where ongoing rainfall is itself weakening for the same reason. HREF guidance shows about a 30% chance of exceeding FFGs across portions of the area for both 3 and 6 hour FFGs. Wegman ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...ARX...DMX...DVN... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 43489301 43459282 42679163 41369227 41169347 41199471 41859507 42539488 43179433 43459369