Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 23 2023 08:09:28 FOUS30 KWBC 230809 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 408 AM EDT Thu Mar 23 2023 Day 1 Valid 12Z Thu Mar 23 2023 - 12Z Fri Mar 24 2023 ....THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL OVER A PORTION OF THE MID/SOUTHERN MISSISSIPPI VALLEY.. An abundant, steady stream of Gulf moisture as a deep-layer trough ejects from the Southern Rockies and results in strengthening low level flow. At about the same time, upper level divergence from an upper level jet aids in surface low pressure forming along a quasi-stationary front extending from Oklahoma northeastward into the Ohio/Tennessee Valley. Precipitable water values at or slightly greater than 1.25 inches reaches eastern Oklahoma by 23/18Z before becoming more expansive by 24 00Z, from Texas to Kentucky. Strong moisture convergence along the boundary along with support from the upper level jet will aid in the production of moderate to locally heavy rainfall, especially from eastern Oklahoma to the southern Indiana. There still potential for 1 to 2 inch/hour rain rates during the afternoon, but especially by/after 00Z. While this area is not as saturated as it was a couple of weeks ago...there is local concern given that ground conditions are still fairly moist. The Moderate and Slight Risk areas were expanded to the southwest across Oklahoma to reflect the latest trends in the guidance and WPC QPF. Campbell Day 2 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 continue from the day 1 period in proximity to the sprawling frontal boundary with moisture flux convergence increasing 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. By 25/00Z a PW fetch of 1.5 inches will span from the Gulf Coast to the MO boot heel, feeding right into the frontal boundary, which is some (+2 to +2.5 standard deviations greater than climatology for late March.=20 Repeating storms will track across areas soaked from recent rains and will likely surpass local FFGs early into the Day 2 period. The latest model runs have been persistent with areal averages of 2 to 4+ inches with above average confidence. This part of the nation will be sensitive to additional rainfall, let alone a large area with several inches of new accumulations. The Moderate Risk area was adjusted a little to the southwest.The Slight Risk was expanded a smidgen toward the Oklahoma/Arkansas border while trimmed northward across northern Mississippi and Alabama. The Marginal Risk area was also trimmed northward across the Lower Mississippi Valley. Campbell Day 3 Valid 12Z Fri Mar 24 2023 - 12Z Sat Mar 25 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_baoh9oat4GtAS0UKRrcEhlhOpVEP0s4hpeCbNJWFZk_= JkuT61FVp5KYnlLs37_nh77mld7jw9XnfKS4IqJBgcY-P7Q$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_baoh9oat4GtAS0UKRrcEhlhOpVEP0s4hpeCbNJWFZk_= JkuT61FVp5KYnlLs37_nh77mld7jw9XnfKS4IqJBJ6p0dGw$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_baoh9oat4GtAS0UKRrcEhlhOpVEP0s4hpeCbNJWFZk_= JkuT61FVp5KYnlLs37_nh77mld7jw9XnfKS4IqJBSPHMvDU$=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) .