Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Mar 03 2024 08:15:37 FOUS30 KWBC 030815 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 314 AM EST Sun Mar 03 2024 Day 1 Valid 12Z Sun Mar 03 2024 - 12Z Mon Mar 04 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Hurley Day 2 Valid 12Z Mon Mar 04 2024 - 12Z Tue Mar 05 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY TO THE CENTRAL GULF COAST... 00Z guidance continues to show showers and thunderstorms developing on Monday and growing upscale in areal coverage and rainfall rates from Monday night into early Tuesday. Shortwave energy will spread into the Lower MS Valley and Central Gulf Coast region in association with an elongated southern stream jet sweeping eastward along the U.S. border with Mexico. This allows for increasing flow of Gulf moisture at low levels to be drawn inland. One concern continues to be that moisture flux standard anomalies barely exceed 1 standardized anomaly greater than climatology, but precipitable water values at or above 1.75 inches and MUCAPEs on the order of 1000 J/Kg per kg hugging the Gulf coast suggests localized rainfall rates of 2-3 inches within 2-3 hours possible, especially where quasi-linear segments off the Gulf train. This scenario could pose an isolated flash flood risk, mainly across urban and other poor-drainage areas. As a result, only minor tweaks were made to the previously issued Marginal Risk area, mainly to shift the outlook a little farther westward given the slightly slower trends per the non-CMC guidance. Either way, the forecast confidence remains low given the continued high spread with the model QPFs (both placement and timing). Hurley/Bann Day 3 Valid 12Z Tue Mar 05 2024 - 12Z Wed Mar 06 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF THE SOUTHEAST AND CENTRAL-EASTERN GULF COAST... The southern stream shortwave trough across the Central Gulf Coast region early Tuesday will become more negatively tilted as it pivots across the Southeast and southern Appalachians later Tuesday and Tuesday night. The shortwave energy aloft and surface low/associated fronts will be fairly progressive, which again is a contributing factor in the more limited (Marginal) excessive rainfall threat as with the Day 2 outlook. 850-700 mb moisture flux anomalies peak between 1-1.5 standard deviations above normal per the GEFS, while PWs climb to ~1.75" along/near the coast. Availability of deep-layer instability is a bit more nebulous given the lack of model consensus, while the relatively progressive synoptic features point to a more limited excessive rainfall threat. However, the rapid increase in deep-layer moisture (TPW standardized anomalies reaching +2 per the GEFS) would support the potential for rainfall rates of 2-3+" in 2-3 hours where convective segments can align and train. Hurley =20 Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_9yu65I3FOyHYw3yCd20pmU1EVfNXzeOrrE1PuT-v3nb= 33yievTYiGg3iAJqwuFZC1o-g6M_548BGntP_IUQSDk9pXU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_9yu65I3FOyHYw3yCd20pmU1EVfNXzeOrrE1PuT-v3nb= 33yievTYiGg3iAJqwuFZC1o-g6M_548BGntP_IUQ4ivxpZM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_9yu65I3FOyHYw3yCd20pmU1EVfNXzeOrrE1PuT-v3nb= 33yievTYiGg3iAJqwuFZC1o-g6M_548BGntP_IUQozrKsRU$=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) .