Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Nov 30 2023 07:56:56 FOUS30 KWBC 300756 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 256 AM EST Thu Nov 30 2023 Day 1 Valid 12Z Thu Nov 30 2023 - 12Z Fri Dec 01 2023 ....THERE IS A SLIGHT RISK AREA FOR PORTIONS OF THE CENTRAL GULF COAST... A Slight Risk area was raised for portions of the Southeast Texas Coast to south-central Louisiana. The latest guidance has persisted with the focal point of convection and flash flood concerns across east Texas into the western half of Louisiana where instability maximum for the period will be co-located within the best ascent from our passing shortwave trough to the north and surface convergence within the confines of a propagating cold front. Hourly rates of 1 to 2.5+ inches/hour is projected to focus across this stretch of the coast and lifting north/northeast through the entirety of this period. Parts of this region have been drier of late and rain will be beneficial, at least initially. Rainfall efficiency ramps up by 00Z and with multiple hours with rates over 1.5/2 inches/hour could quickly reach or exceed local flash flood guidance leading to isolated/scattered areas with flooding concerns. The prospect for supercell generation across east Texas given the deep shear profiles and backing low-level wind field off the Gulf will yield some enhanced rainfall within the Storm Prediction Center's Enhanced/Slight severe storm risks respectively. Later in the period, convergent signature along the leading edge of an advancing cold front will act as a focal point for a line of heavy thunderstorms to move eastward across the Louisiana/Texas border into the central portion of Louisiana. Further north some shallow convection will develop across the Ozarks region however amounts will largely be in the 0.75-1.5" territory, and likely over an extended period of time. Isolated areas could develop flooding concerns therefore maintained the Marginal Risk for this part.=20=20 Campbell/Kleebauer =20 Day 2 Valid 12Z Thu Nov 30 2023 - 12Z Fri Dec 01 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL/EASTERN GULF COAST AND THE SOUTHEAST... The area of convection from day 1 will shift east along the Gulf Coast into western portions of the Southeast U.S. Convergence along an approaching cold front within the confines of a anomalously moist environment will generate locally heavy rainfall with flash flood concerns over any urbanized settings. The primary focus has been over southern Alabama into the Florida Panhandle where the instability axis will be greatest and convective regimes could produce 1-2 inches/hour rainfall with locally up to 3 inches/hour near the coastal areas. The latest guidance suggested a small shift in the QPF axis northward further into central Alabama which in turn caused an uptick of QPF for eastern Louisiana. A growing consensus of somewhere within the Marginal bounds could pick up 3-5 inches of rainfall over the course of the period. The Marginal Risk that was already in effect largely covers the area of concern. With the northward trend in the latest guidance and WPC forecast, the western bounds of the Marginal was expanded to include parts of southeast Louisiana and northward across eastern Alabama/western Georgia. Campbell/Kleebauer Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6ccNIdxNGKZuAaa5Ao-T5Supo-bar2deI2mZTUYuHvYj= pi1Iv2wbatv4ob6RyyT5Yd3-Mxlag8KjtPfwInktUMuycjk$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6ccNIdxNGKZuAaa5Ao-T5Supo-bar2deI2mZTUYuHvYj= pi1Iv2wbatv4ob6RyyT5Yd3-Mxlag8KjtPfwInktrnY7gAw$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6ccNIdxNGKZuAaa5Ao-T5Supo-bar2deI2mZTUYuHvYj= pi1Iv2wbatv4ob6RyyT5Yd3-Mxlag8KjtPfwInktAm-xlsc$=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .