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Flash Flood Guidance
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Issued by NWS
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374 AWUS01 KWNH 171708 FFGMPD MSZ000-LAZ000-172305- Mesoscale Precipitation Discussion 0453 NWS Weather Prediction Center College Park MD 107 PM EDT Mon Jun 17 2024 Areas affected...South-Central to Southeast LA...Far Southwest MS Concerning...Heavy rainfall...Flash flooding possible Valid 171705Z - 172305Z SUMMARY...Locally slow-moving and occasional back-building of showers and thunderstorms with very heavy rainfall rates may result in some flash flooding concerns going through the afternoon hours. DISCUSSION...The midday GOES-E Day Cloud Phase RGB in conjunction with dual-pol radar shows an area of convection generally tending to grow in coverage across areas of south-central to southeast LA, and far southwest MS. The activity is being facilitated by increasing low-level convergence along the leading edge of an inverted surface trough crossing the central Gulf Coast region. This coupled with increasing boundary layer instability and very moist southeast flow coming in off the Gulf of Mexico will likely further encourage an expansion of convection over the next few hours. Additionally, the upper-level flow pattern is becoming increasingly diffluent aloft in connection with the area of disturbed weather over the central and southern Gulf of Mexico. MLCAPE values of 1500+ J/kg with PWs of 2.0 to 2.25 inches will drive very heavy rainfall rates with the organizing clusters of convection. Rainfall rates with the stronger storms are forecast to locally reach 2 to 2.5 inches/hour, and with a set-up that is conducive for back-building and repeating convective cells, some localized storm totals going through late this afternoon may reach 3 to 5 inches, and this is consistent with the 12Z HREF guidance. Some isolated to widely scattered instances of flash flooding will be possible, and this will include a localized urban flash flood concern. Orrison ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...JAN...LCH...LIX...SHV... ATTN...RFC...LMRFC...NWC... LAT...LON 31889179 31819089 31168957 30488929 29958943 29738967 29519063 29739180 30219264 30899278 31449255