Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Oct 09 2023 20:08:29 FOUS30 KWBC 092008 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 407 PM 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... ....2000Z Update... Some minor adjustments were made to the northern extent of the SLGT risk across South TX to align with the latest WPC forecast and ensemble-bias corrected QPF field. Elevated moisture stemming from the remnants of TS Max crossing through MX and the northeastern extent of the moisture associated with TS Lidia will allow for an efficient, warm rain process-driven heavy rain event across the outlined area. Despite the limited convective nature of the precip given the lack of overall instability, the well-above normal PWATs expected and overall QPF forecast will allow for localized flash flooding concerns within the urban corridors located along the RGV and TX Gulf coast. Some guidance is fairly bullish on the total QPF footprint with a majority of the precip falling within the 12 hr time frame from 00-12z Wednesday. In coordination with the local WFOs (CRP/BRO), will maintain the SLGT risk in place with only an adjustment on the northern periphery of the risk area based on the recent trends in guidance. Kleebauer ....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 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!-pjJyHVFN-RMALZ_aUYgl-_2oSJJgo5j5XTxKedK8vED= SDN4q0GBR6UlACrZpzqrI9qRubAfTzkdV6F5-ZaMqpgygdI$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-pjJyHVFN-RMALZ_aUYgl-_2oSJJgo5j5XTxKedK8vED= SDN4q0GBR6UlACrZpzqrI9qRubAfTzkdV6F5-ZaMSkThhSA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-pjJyHVFN-RMALZ_aUYgl-_2oSJJgo5j5XTxKedK8vED= SDN4q0GBR6UlACrZpzqrI9qRubAfTzkdV6F5-ZaMmiBQfxw$=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) .