Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Nov 12 2023 19:52:24 FOUS30 KWBC 121952 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 251 PM EST Sun Nov 12 2023 Day 1 Valid 16Z Sun Nov 12 2023 - 12Z Mon Nov 13 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHERN TEXAS... Deep southwesterly mid-to-upper level flow ahead of a low/trough moving across northwestern Mexico and the southwestern U.S. will combine with strengthening low level easterly winds to support increasing moisture across Deep South Texas. Model soundings show deep saturation through the column, with PWs climbing to around 2 inches from the lower Texas Coast back into the Rio Grande Valley later today. This moisture interacting with increasing ascent afforded by mid level energy and favorable upper jet forcing will support organized rainfall and the potential for locally heavy rainfall totals across the region. Models continue to indicate that a lack instability will diminish the potential for heavy rainfall rates. However, a deep warm cloud layer and saturation through the low to mid levels will likely support efficient rates and the potential for runoff concerns, especially in poor drainage and urbanized areas. For the Day 1 update after coordination with the affected WFOs and the National Water Center, the Slight Risk area across Deep South Texas has been dropped with just a slightly larger Marginal Risk area encompassing the central and southern Texas Gulf Coast.=20 Although 1-2 inches of additional rainfall is possible here today per recent model guidance, and even higher just offshore, the lack of onshore instability is really capping rainfall rates and thus mitigating the potential for flooding. Hamrick/Pereira=20 Day 2 Valid 12Z Mon Nov 13 2023 - 12Z Tue Nov 14 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE MIDDLE TEXAS COAST TO SOUTHERN LOUISIANA... As the previously noted mid-to-upper level trough/low continues to move east, models show a surface low developing along a lingering frontal boundary over the northern Gulf, with the surface wave tracking slowly from the northwestern to the north-central Gulf on Monday into Monday night. Deep southerly flow ahead of the wave will direct increasing moisture into an area of large-scale ascent, supporting organized and potentially heavy rainfall from the middle Texas Coast to southern Louisiana. Limited instability will remain a mitigating factor however, with models indicating that the greater instability and threat for heavy rainfall rates will remain mostly out over the Gulf. However, efficient rates supported by deep warm cloud layers and saturation through the low to mid levels may generate some localized runoff concerns, especially if prolonged periods of rain occur over poor drainage and urbanized areas.=20 For the 12Z update, the existing Marginal Risk area has been maintained with no need for any upgrade to a Slight Risk. The latest CAM guidance strongly supports the core of the heaviest convection should remain offshore, closer to the surface low and where the best instability will reside. The Marginal Risk is generally from the Interstate 10 corridor southward to the Gulf Coast. There was a slight westward extension of the outlook area to include the Corpus Christi area, where the ARW2 and NAM conest have some lingering heavy rainfall close to the Texas Coast in that area.=20 Hamrick/Pereira Day 3 The Day 3 outlook will be updated by 2030Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!94XeDUps6_hpOdyN7Iryfxc2QoNRMpf41LO4bb1jTIMR= V6yDnPqVYAh0G5-9er-86zlHYWoilBv2v79VOnWIQseXicQ$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!94XeDUps6_hpOdyN7Iryfxc2QoNRMpf41LO4bb1jTIMR= V6yDnPqVYAh0G5-9er-86zlHYWoilBv2v79VOnWIhNI7CgA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!94XeDUps6_hpOdyN7Iryfxc2QoNRMpf41LO4bb1jTIMR= V6yDnPqVYAh0G5-9er-86zlHYWoilBv2v79VOnWI_hU2SZA$=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) .