Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Dec 04 2024 00:23:15 FOUS30 KWBC 040022 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 722 PM EST Tue Dec 3 2024 Day 1 Valid 01Z Wed Dec 04 2024 - 12Z Wed Dec 04 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTH TEXAS... ....01Z Update... The Marginal Risk area for portions of South TX will be maintained for the overnight period, with mainly the coastal areas including=20 Padre Island seeing the greatest threat still for some heavier=20 shower activity. Overall, the threat should tend to lessen overnight with the guidance suggesting any more organized and focused rains staying offshore. However, with surface low pressure noted in very close proximity to Padre Island helping to focus an axis of somewhat strong moisture convergence and an instability gradient along the coast, there may be some locally heavy showers=20 that still develop and support some spotty 2 to 3+ inch rainfall=20 amounts overnight. Thus, any impacts are expected to be highly=20 isolated. Orrison Day 2 Valid 12Z Wed Dec 04 2024 - 12Z Thu Dec 05 2024 ....Western Gulf Coast... Convection is expected to move through portions of eastern TX and LA near a weak area of baroclinic low pressure. While some instability exists near the Upper TX Coast (500+ J/kg of CAPE), the 850 hPa inflow is veering which along with the cyclone's progression argues for convective progression. Precipitable water values are expected to lie mainly in the 1.5-1.75" range. Effective bulk shear and low- level inflow appear sufficient for some level of convective organization, but the progression should keep heavy rainfall modest. The 12z Canadian Regional has local maxima in the 4"+ range within LA, the 12z ECMWF has backed off the amounts it advertises across southwest LA. The 12z mesoscale guidance wasn't emphatic on the heavy rain prospects, showing pockets of 20-30% chance of 3"+ amounts. As flash flood guidance values are high due to minuscule rainfall over the past week, the rainfall expected is expected to be mostly welcome and not a significant flash flood concern. While the threat of flash flooding is non-zero should convection train or backbuild, which could lead to 2" an hour totals should it happen, any occurrences would be isolated at best, and the probability of rainfall exceeding flash flood guidance is still considered to be less than 5 percent. Roth Day 3 Valid 12Z Thu Dec 05 2024 - 12Z Fri Dec 06 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Roth/Wegman Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7RSVcglKshhtVVFcFMJb7fALOpDX2ItwPGw5OXx1-L6X= sI3Mrdhn09VNrnnegsA-q0bQUfywdU1DNqtvDjFJ0qGgPIM$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7RSVcglKshhtVVFcFMJb7fALOpDX2ItwPGw5OXx1-L6X= sI3Mrdhn09VNrnnegsA-q0bQUfywdU1DNqtvDjFJpprqzlI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7RSVcglKshhtVVFcFMJb7fALOpDX2ItwPGw5OXx1-L6X= sI3Mrdhn09VNrnnegsA-q0bQUfywdU1DNqtvDjFJNtPVzNo$=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) .