Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Oct 09 2023 15:40:25 FOUS30 KWBC 091540 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1139 AM EDT Mon Oct 09 2023 Day 1 Valid 16Z Mon Oct 09 2023 - 12Z Tue Oct 10 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Pereira/Kleebauer Day 2 Valid 12Z Tue Oct 10 2023 - 12Z Wed Oct 11 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTH TEXAS... ....South Texas... An amplifying trough moving across the southwestern U.S. and northwestern Mexico is expected to direct the remnant energy associated with Tropical Storm Max, followed quickly by energy associated with Tropical Storm Lidia, across northern Mexico.=20 Moisture associated with these systems in addition to increasing low level southerly flow ahead of a wave lifting through the northwestern Gulf of Mexico will support steadily rising PWs across the region on Tuesday. Guidance shows PWs climbing to 2-2.5 inches (2-3 standard deviations above normal) along a low level boundary lifting north along with the wave. This deep moisture, along with large-scale ascent afforded in part by right-entrance region upper jet forcing, will likely support the development of heavy precipitation across parts of the area. With plenty of differences in the details, guidance generally indicates two areas of heavy amounts -- one inland across southern Texas in the vicinity of the better mid-to-upper level forcing; and a second area near the coast and the developing surface wave.=20 Models disagree as to how far, if at all, this second area will develop and spread inland. While confidence in the details is limited, still felt there was enough of a model signal to maintain a Slight Risk across portions of the region, with the potential for excessive rain remaining a concern especially across urbanized areas and areas impacted by recent rains. Pereira Day 3 Valid 12Z Wed Oct 11 2023 - 12Z Thu Oct 12 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ALONG PORTIONS OF CENTRAL GULF COAST... ....Central to the eastern Gulf Coast... Low pressure moving into the northwestern Gulf of Mexico is forecast to track east with a warm front and corresponding pool of deep moisture lifting out ahead of it. Strong, deep southwesterly flow into the boundary will support PWs of 2-2.25+ inches spreading north into the region. In addition to the deep moisture, right-entrance region upper jet forcing will remain a factor as well -- supporting large-scale ascent and the development of organized precipitation within the region. While the overall setup is favorable for at least locally heavy amounts, confidence regarding their placement is less than average. The axis of heaviest amounts and the greater threat for flash flooding will be at least partially dependent on the timing of the wave and on the placement of the warm front. While warm rain processes will likely support efficient rain processes, limited instability north of the front will help to keep rain rates in check, limiting the flooding threat for those areas, especially given the dry antecedent conditions that cover much of the region. Heavier rain rates are expected along and south of the front. Given what is expected to become a fairly amplified wave, the front is expected to lift at least partially inland with heavy amounts along the coast. Therefore, a Slight Risk was introduced along the coast from southeast Louisiana to the Florida Panhandle. However, given the overall uncertainty regarding the timing of the wave and the placement of the warm front, significant adjustments may be required in future updates. ....Mid Mississippi Valley... Potentially heavy rain may develop across the region as an upper low develops and drops southeast across the central Rockies into the Plains. Amplifying southerly flow into a slow-moving boundary ahead of the low will produce increasing PWs into an area of strong lift supported by a favorable upper jet couplet. This may result in some localized heavy amounts centered across Iowa into northern Illinois beginning by late Wednesday and continuing into the overnight. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8jpe9t_VkicI7GVWFg9XieXP4wehJ5qN0QXhYGQd45qE= QOvwniExFW2PLPQe1UYXt9GrrLg5zfVIa4wSFZ6IBRCo1A4$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8jpe9t_VkicI7GVWFg9XieXP4wehJ5qN0QXhYGQd45qE= QOvwniExFW2PLPQe1UYXt9GrrLg5zfVIa4wSFZ6IWw_QAjc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8jpe9t_VkicI7GVWFg9XieXP4wehJ5qN0QXhYGQd45qE= QOvwniExFW2PLPQe1UYXt9GrrLg5zfVIa4wSFZ6INB7g-mc$=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) .