Flash Flood Guidance
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Issued by NWS
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310 AWUS01 KWNH 100124 FFGMPD MSZ000-LAZ000-ARZ000-TXZ000-100630- Mesoscale Precipitation Discussion 0254 NWS Weather Prediction Center College Park MD 923 PM EDT Thu May 09 2024 Areas affected...Western & Central MS...Northern LA...Far Eastern TX... Concerning...Heavy rainfall...Flash flooding possible Valid 100125Z - 100630Z SUMMARY...Deep layer flow parallel to the front with weak but sufficient perpendicular convergence at cloud layer with ample deep moisture may promote training of intense rainfall resulting in localized 2-4" totals and possible flash flooding. DISCUSSION...Boundary layer decoupling is occurring along slowly southward sagging cold front across NE TX, N LA into N MS. Highly unstable and deeply rich moisture content is converging weakly due to southerly 850mb flow at 10-15kts but generally orthogonal to the boundary and with reduced capping at dusk, the convergence is sufficient to break out thunderstorms. MLCAPE of 3500-4000 J/kg and Tds in the upper 70s allowing for TPW of 2" will support intense rain cores of 2"/hr even with limited moisture flux on the southerly inflow. Generally, the area is in a solid stretching/shearing boundary that supports this convergence in the low levels with stronger flow aloft between exiting wave to northwest and deepening wave over central TX. As such, steering flow is strong but parallel to allow for training profiles of the stronger convection. Additionally with weak inflow, propagation vectors align with the 500-1000 thickness pattern gradient parallel to the deformation zone and will support training profiles initially. Given the moist profile, slow cold pool generation will occur and allow for some duration for the training. Eventually, they will form and either the convection will propagate southeastward or a new cycle of updrafts will form along it. As such, streaks of 2-4" are going to possible mainly in a 2-3 hour period. Given the higher FFG and recently dry conditions, scattered incidents of flash flooding may be possible through the early overnight period. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...JAN...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 33239056 33218920 31668912 31459000 31519166 31559280 31219416 31459474 32069481 32279436 32779241