Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 22 2023 15:53:14 FOUS30 KWBC 221553 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1152 AM EDT Wed Mar 22 2023 Day 1 Valid 16Z Wed Mar 22 2023 - 12Z Thu Mar 23 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHERN CALIFORNIA AND CENTRAL ARIZONA... Maintained the on-going Marginal Risk area for portions of southern California and central Arizona. Additional rainfall is expected on and off throughout the day and into the evening across this area as an upper low initially along the central California coast fills and the lingering trough axis with cold temps aloft tracks into the Desert Southwest later tonight. The latest HRRR and ARW both generate upwards of 500 J per kg of surface-based CAPE during the afternoon as low/mid level lapse rates steepen while moisture continues to be transported inland by west to southwest flow at 15 to 30 kts. Additional rainfall of an inch or so (mainly focused in/near the terrain) will be falling on areas that are already hydrologically sensitive to additional precipitation.=20 Bann Day 2 Valid 12Z Thu Mar 23 2023 - 12Z Fri Mar 24 2023 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FROM THE SOUTHERN PLAINS TO THE OHIO VALLEY... A steady stream of Gulf of Mexico moisture will surge northward along a frontal boundary spanning from the Great Lakes region southwest to New Mexico and produce widespread rain from the Southern Plains to the Ohio Valley. Low level flow transporting PW values of 1.25 (+2 std dev) into the heart of the nation will be nearly parallel to the frontal boundary. A southwest to northeast orientated swath of QPF is expected to setup from Texas to Pennsylvania with some of the highest amounts aligning in a narrow band from eastern Oklahoma to Indiana. The 3-hr FFGs across the general area are 1.5/2 inches with areal averages of 1 to 3+ inches forecast. There were already Slight and Marginal Risks for excessive rainfall in effect. Given the latest trends and WPC QPF, the Marginal Risk and Slight Risk areas were expanded south and west across parts of Oklahoma, Texas and Louisiana. The Marginal Risk was expanded a few counties southward from eastern Kentucky to West Virginia. The eastern bounds of the Slight Risk was narrowed a bit to be near/south of I-70 in Indiana and Ohio. Campbell Day 3 Valid 12Z Fri Mar 24 2023 - 12Z Sat Mar 25 2023 ....THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL FROM THE OZARKS TO THE OHIO VALLEY... Showers and thunderstorms will persist from the day 2 period in proximity to the sprawling frontal boundary. Moisture convergence will increase across parts of the Mississippi Valley and into the Ohio Valley as a surface low pressure with trailing cold front moves east across the Southern Plains. PW values will surge up to 1.5 inches (+2 to +2.5 Std dev) into the Mississippi/Tennessee/Ohio Valleys. Repeating storms will track across areas soaked from recent rains and will likely surpass local FFGs early into the D3 period. The latest guidance depicts several inches of rain to fall in a SW to Northeast orientation with above average confidence. The EC ensemble means are showing a sizable area from Arkansas to Ohio with a 20% probability of exceeding 3 inches with a few speckles that have a 5% probability of 5 or more inches of rain in a 24 hour period. This part of the nation will be sensitive to additional rainfall, let alone a large area with several inches of new accumulations. A Moderate Risk area for excessive rainfall and flooding is now in effect from northeast Arkansas to western Ohio. A Slight Risk stretches from the Arkansas/Louisiana border to western Pennsylvania. A Marginal Risk area covers eastern Texas to western Maryland. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7EINH4Wc45A8q7rPOr0cGADEDuEO88QMq0SVVu24nWiV= G4neH8xvdUAGYWc1pfWAVLpILnfwd0lOYIgRtx_EWJy5nNU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7EINH4Wc45A8q7rPOr0cGADEDuEO88QMq0SVVu24nWiV= G4neH8xvdUAGYWc1pfWAVLpILnfwd0lOYIgRtx_EwB4Oa0w$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7EINH4Wc45A8q7rPOr0cGADEDuEO88QMq0SVVu24nWiV= G4neH8xvdUAGYWc1pfWAVLpILnfwd0lOYIgRtx_EYPmpVoc$=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) .