Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Dec 01 2023 08:27:28 FOUS30 KWBC 010827 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 326 AM EST Fri Dec 01 2023 Day 1 Valid 12Z Fri Dec 01 2023 - 12Z Sat Dec 02 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL GULF COAST... Surface troughing over the Gulf will develop ahead of a stationary front over TX. Return flow east of the front will advect an air mass with PWATS approaching 2 inches into the central Gulf coast, pushing north into the Tennessee Valley as a warm front by early Saturday morning. Meanwhile in the upper levels a nearly stationary but strengthening jet streak will form over the stationary front in response to the large gradient in temperature and moisture across the front. Thunderstorms ongoing across the Deep South will diminish through the morning, with redevelopment of showers and storms from late afternoon through the overnight. Instability in the warm and moist air mass will be between 1,000 and 1,500 J/kg...which is capable of supporting training storms near the Gulf. There's considerable uncertainty as to how far north that instability will get as the storms track from the Gulf into the coast. Due to the time of year, disagreement in the guidance, high FFGs, and limited forcing over the Tennessee Valley, the greatest chance of isolated flash flooding should be near the coast, particularly in any urban areas. The pattern is likely to evolve similarly to today, albeit further east, with the potential for training thunderstorms capable of 3 inch per hour rates in the Marginal Risk area. Thus, the Marginal risk was trimmed southward to focus on the urban areas of the central Gulf Coast from near Houston through Pensacola. Given the above limitations further inland, the storms appear unlikely to have the support needed to produce those rainfall rates. The strengthening jet streak should also help to keep the storms moving quickly the further away from the Gulf Coast they get. Wegman 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!_mM-m-eg982DzNQMWsbgX63Zre6sEu0E65wxNPtS1kyA= 8OVfzCyki_5nwTPrNLVU2MHklKtQqurZf3BB5yH46ObvCOk$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_mM-m-eg982DzNQMWsbgX63Zre6sEu0E65wxNPtS1kyA= 8OVfzCyki_5nwTPrNLVU2MHklKtQqurZf3BB5yH4R2ZvzWk$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_mM-m-eg982DzNQMWsbgX63Zre6sEu0E65wxNPtS1kyA= 8OVfzCyki_5nwTPrNLVU2MHklKtQqurZf3BB5yH4Iz5Fhpo$=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) .