Subj : MESO: Heavy Rain - floodi To : All From : Mike Powell Date : Wed Jul 12 2023 07:36:00 AWUS01 KWNH 121124 FFGMPD MSZ000-LAZ000-ARZ000-TXZ000-121500- Mesoscale Precipitation Discussion 0705...Corrected NWS Weather Prediction Center College Park MD 723 AM EDT Wed Jul 12 2023 Corrected for flash flooding tag Areas affected...Southern Arkansas... Northern Louisiana...Adj Far NE Texas...Northwest Mississippi... Concerning...Heavy rainfall...Flash flooding likely Valid 121122Z - 121500Z SUMMARY...Extreme rain-rates and totals pressing 8-10" in portions of Southwest Arkansas will continue to produce significant flash flooding. Scattered downstream cells into NW MS may have 2-3"+ and isolated lower end flash flooding thru 15z. DISCUSSION...GOES-E 1-minute 10.3um EIR shows MCC across southern AR with two main cooling/overshooting tops (-75C). RADAR depicts this a a mature arc of convection from Desha/Drew to Bradley and then back to Miller/Lafayette county. Evolution of the MCC depicts the combination of MCV and parent mid-level shortwave near Cleveland county lifting northward. DPVA and low level moisture convergence from southwesterly overrunning is becoming increasingly distant from pool of instability across NE TX into N LA, but given deep 2.25-2.5" total PWats and deep warm layer, rainfall efficiency has been strong to support 2-2.5"/hr rates. Forward (northeast) cell motion ahead of the shortwave and weak propagation should maintain a more scattered appearance lifting into NW MS over the next few hours, spots of 2-4" are possible in an hour or two and may result in possible flash flooding, but more scattered in nature relative to the upwind edge of the complex, so have extended the MPD into NW MS on this lower-end risk. RADAR trends show a bit more southward propagation of the upwind edge of the MCC across SW AR. CIRA LPW denoted a small wedge of drier air across SW OK that may have mixed into the mid-levels to allow for increased cold pool generation over the last few hours. However, 850-700mb moisture channel appears to becoming increasingly confluent/convergent in the vicinity of Hempstead county allowing for continued backbuilding and with 2.5" total PWat values along 20kt southwesterly 850mb flow (64 to 68F Tds) veering to 25-30kts at 700mb (45-50F Tds) should continue to support efficient rainfall production of 3-3.5"/hr. Southward propagation may alleviate the areas of Ouachita/Nevada/Union counties of receiving more rain, but localized totals of 8-10" remain probable even with some southward propagation, though more likely a broader area of 4-6" will occur perhaps into the first row of NW LA parishes. Flash flooding is likely to continue with some rural spots experiencing significant flooding still through the early morning hours (14-15z). Gallina ATTN...WFO...JAN...LZK...MEG...SHV... ATTN...RFC...ABRFC...LMRFC...NWC... LAT...LON 34669058 34318998 33799002 33269050 32669156 32489247 32659353 33299433 33889441 34439431 34379367 33779293 33769238 33949188 34339152 34589122 = = = --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .