Subj : HVYRAIN: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Oct 05 2023 07:44:30 FOUS30 KWBC 050744 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 343 AM EDT Thu Oct 05 2023 Day 1 Valid 12Z Thu Oct 05 2023 - 12Z Fri Oct 06 2023 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF SOUTH TEXAS AND THE WESTERN AND CENTRAL GULF COASTAL PLAIN... A high amplitude long wave trough will continue to progress across the central US into the Midwest/Mississippi River Valley today with an attendant cold front that will be the main driving focus for shower and thunderstorm activity from the Great Lakes to the Southern Plains. Further north, across SE Missouri to Southern LP of Michigan there may some sections particularly across IL and N IND that may have longer duration moderate showers/thunderstorms that may result in longer term 2-3" totals though flooding potential remains below a categorized risk level today mainly driven by lack of instability (~250 J/kg) and deeper layer moisture values (1.0-1.33") to drive intense short-term rain rates necessary for flash flooding concerns. Further south, a much deeper moisture and conditionally unstable environment will precede the cold front. At the start of the period, there appears to remain some potential for some localized ongoing flash flooding across northern and northeast TX, though the shortwave energy at the base of the larger scale trough has started to stretch more positively tilted and become more progressive driving forward (southward) propagation of thunderstorm activity toward the Coastal Plain, angling back over the lower Edwards Plateau/Hill County into South Texas. Ample deep layer moisture of 2-2.25" of Total PWats and 1500 J/kg to 750 J/kg will exist from the Lower Rio Grande toward the southern Triangle/Piney Woods region of eastern TX; maintaining the risk of short-term but very intense rainfall rates in excess of 2"/hr (HREF probability remain 25-50% through out the morning into early afternoon hours. While the front and propagation may be fast southward, the low level confluent inflow and veering toward southwesterly steering flow, may allow for cells to develop upstream and track back against the forward propagation motion for some enhanced short-duration training/repeating; especially closer to the Middle to Upper Texas Coast where 00z Hi-Res guidance and 00z HREF suggest localized spots of 2-4".=20 A secondary axis of enhanced rainfall risk will be along (more likely west of) the Rio Grande River, as channeled return moisture flow responds to the farthest tail-end of shortwave energy.=20 Pooled moisture convergent along the Serranias del Burro mountains may trigger stronger scattered thunderstorms that are probable to track along and south through the Valley increasing potential for scattered 2-3" totals and similar widely scattered flash flooding potential mainly prior to 06.03z.=20 Downstream into the central Gulf Coast...as the early morning convection wanes, the front will continue progress eastward into the Lower Mississippi River Valley, while the deeper moisture from the Western Gulf will not be accessible, lingering moderate to above average moisture will continue to be transported through the Central Gulf and intersect with the approaching front generally around 1.5-1.75" total PWATs. Fairly clear skies should allow for some insolation to destabilize with Hi-Res CAMs suggesting 1000-2000 J/kg of CAPE are possible SE LA in the late evening hours. As such, there has been some increasing signal for potential for intense but more scattered thunderstorms across the central Gulf coast in the late evening hours. Widely scattered incidents of 3-4" are not out of the realm of possibility and given proximity to some urban locations, have decided to expand the Marginal Risk of Excessive Rainfall eastward to generally Mobile Bay to account for this scenario. Gallina Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5ByaOy7jcWQD9wPTghz3sj8lbUh1uPmB8wlZd3LOaE8I= KhfshWB33XAIhdADFpoXiQjdPWPiy8q4sHde1uEop6E5k_w$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5ByaOy7jcWQD9wPTghz3sj8lbUh1uPmB8wlZd3LOaE8I= KhfshWB33XAIhdADFpoXiQjdPWPiy8q4sHde1uEonbKmbAo$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5ByaOy7jcWQD9wPTghz3sj8lbUh1uPmB8wlZd3LOaE8I= KhfshWB33XAIhdADFpoXiQjdPWPiy8q4sHde1uEoVTbsyIE$=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) .