Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Apr 07 2024 15:22:25 FOUS30 KWBC 071522 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1122 AM EDT Sun Apr 7 2024 Day 1 Valid 12Z Sun Apr 07 2024 - 12Z Mon Apr 08 2024 Rainfall is not expected to exceed flash flood guidance. Campbell Day 2 Valid 12Z Mon Apr 08 2024 - 12Z Tue Apr 09 2024 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN PLAINS AND ADJACENT SOUTHERN MISSISSIPPI VALLEY... The potential for heavy to excessive rainfall looks to develop over portions of the southern U.S. as shortwave energy diving southward over the Intermountain region helps carve out a deep layer southern stream trough. Flow aloft over the Slight Risk area backs and begins to accelerate Monday evening and Monday night...with increasingly divergent flow aloft and increasing low level moisture transport helping to set the stage for convection capable of producing downpours. Model guidance has been showing run to run differences in placement and rainfall amounts...with the GFS pretty much on its own scooting one area of heavy rainfall eastward quickly away from Texas/Arkansas/Louisiana into the Tennessee=20 Valley overnight while other guidance tended to be less progressive with the rain. Spaghetti plots from successive runs of both the=20 GEFS and SREF showed some consistency with 2- or 3-inch amounts=20 that was in general agreement with earlier thinking that 2 to 4=20 inches (with isolated higher amounts certainly possible) could=20 fall. With maximum precipitable water values over southeast Texas=20 being in excess of 1.75 inches resulting in an axis of coherent=20 moisture transport that could interact with an old cold front=20 boundary...the idea of heavy rainfall capable of producing flooding is reasonable although some uncertainty remains. Bann Day 3 Valid 12Z Tue Apr 09 2024 - 12Z Wed Apr 10 2024 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE SOUTHERN MISSISSIPPI VALLEY... Heavy to potentially excessive rainfall should be on-going at the beginning of the outlook period on Tuesday morning that persists into the daytime hours. Flow aloft should be increasingly diffluent east of an approaching deep-layer trough and closed low while=20 moisture from the Gulf continues to be drawn northward. How long it takes for convection to become progressive is one of the main=20 forecast concerns. The GFS continues to be some 12 hours faster=20 than other guidance in when it shunts precipitation south and east. The 07/00Z runs of the ECMWF and Canadian tended to push some=20 isolated maximum totals of 4 to 6 inches well south into Louisiana=20 while the more progressive GFS tended to have smaller maximum=20 values pushing into Tennessee by the end of the outlook period. The real concern is in the 48-hour rainfall totals...with 5 to 7 inch=20 amounts possible embedded within a broader 3 to 5 inch area. With=20 those amounts...hoisted a Moderate Risk area that generally=20 extended across southern Arkansas into northern Louisiana where=20 there was the best overlap of the various guidance. Additional=20 adjustments can be expected...assuming the short-term numerical=20 guidance sorts out timing and placement details. Bann Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!60TljMZq8wHukRKmLgP9aypwBh79_Oy-o0t23sPTOicj= gQBBAsMLMhG_GEXfa55GFnERUMBEkkhn6EExPv1CoEgZMZ4$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!60TljMZq8wHukRKmLgP9aypwBh79_Oy-o0t23sPTOicj= gQBBAsMLMhG_GEXfa55GFnERUMBEkkhn6EExPv1C4CDozxQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!60TljMZq8wHukRKmLgP9aypwBh79_Oy-o0t23sPTOicj= gQBBAsMLMhG_GEXfa55GFnERUMBEkkhn6EExPv1CP0FiW6s$=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .