Flash Flood Guidance
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Issued by NWS
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181 AWUS01 KWNH 280916 FFGMPD TXZ000-OKZ000-281500- Mesoscale Precipitation Discussion 0336 NWS Weather Prediction Center College Park MD 514 AM EDT Tue May 28 2024 Areas affected...southwestern OK into North TX Concerning...Heavy rainfall...Flash flooding likely Valid 280900Z - 281500Z Summary...Heavy showers and thunderstorms will continue to produce 1-3"/hr rainfall rates through mid to late morning, resulting in localized totals of 3-6". Isolated to scattered flash flooding is likely. Discussion...Heavy showers and thunderstorms are becoming more organized along and near the Red River of the South (TX/OK border region) early this morning, following recent backbuilding in the vicinity of right-movers that emerged from earlier splitting supercells. This has already resulted in some localized totals of 2-4" in the region, but additional backbuilding and training of cells is expected to result in an increase in coverage and severity of flash flooding into late morning. The mesoscale environment is highly favorable for additional upscale growth of convective activity, given ample instability (MUCAPE of 2000-5000 J/kg), tropospheric moisture (PWATs of 1.2-1.5 inches, near the 90th percentile per FWD sounding climatology), and shear (effective bulk shear of 45-55 kts). This parameter space should have no trouble continuing to support rainfall rates of 1-3"/hr. While a couple HREF members (ARW and NAM-nest) have a depiction of convection in this region this morning, even those members were far too slow and weak compared to observational trends (while the other members didn`t even manage to initiate convection). The HRRR has come around in the past couple of runs (06z/07z) after insisting on suppressed convection from earlier runs. While the coverage and amounts are likely still at least a bit underdone (indicating localized totals of 2-3" in a limited area of North TX through 15z), the general QPF footprint and storm evolution matches that of the HREF PMM, indicating additional upscale growth towards the southeast via upwind propagation towards the higher instability (and focused along and near a quasi-stationary surface boundary). This puts the Dallas-Forth Worth metroplex in the cross hairs of this mornings activity, increasing concerns for flash flooding (given the sensitivities of the urbanized terrain and higher population centers). Given the highly favorable observational trends (and the unreliability of the hi-res guidance), isolated to scattered instances of flash flooding are likely through late morning (with 3-6 hour FFGS generally 2-4"). Should these higher totals occur across the DFW metroplex, some flash flooding could be locally significant (as 3-hr FFGs locally as low as 1.5"). Churchill ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...AMA...FWD...LUB...OUN...SHV... ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC... LAT...LON 35279874 34919731 34309630 33329564 32479529 32249650 32729746 33489851 34860025