Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Feb 28 2023 03:30:43 FOUS30 KWBC 280330 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1030 PM EST Mon Feb 27 2023 Day 1 Valid 0329Z Tue Feb 28 2023 - 12Z Tue Feb 28 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent.=20=20 Roth Day 2 Valid 12Z Tue Feb 28 2023 - 12Z Wed Mar 01 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent.=20 Orrison Day 3 Valid 12Z Wed Mar 01 2023 - 12Z Thu Mar 02 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF TENNESSEE... ....Mid-South... Low-amplitude southern stream shortwave energy embedded within strong, and increasingly diffluent mid to upper-level west-southwest flow aloft downstream of the longwave trough over the Southwest will be interacting with a quasi-stationary front draped across the Mid-South for multiple rounds of convection late Wednesday afternoon through Wednesday night. The convective threat will be facilitated by an increasingly moist and unstable boundary layer pooling along and south of the front with aid of a 30 to 50 kt low-level jet. PWs are forecast to rise to locally over 1.5 inches over the Mid-South with these values reaching as much as 2 to 3+ standard deviations above the mean. A dual moisture feed regime is forecast with a combination of low-level Gulf of Mexico moisture working in tandem with the northeast transport of mid to upper-level eastern tropical Pacific moisture which is already seen pooling in the latest CIRA-ALPW imagery. MUCAPE values are forecast to rise in the vicinity of the front to between 1000 to 1500 J/kg and this coupled with deep layer forcing associated with the aforementioned shortwave energy, increasing vertical shear, and larger scale placement of right-entrance region jet dynamics/forcing should result in regional development of organized convection. Multiple convective clusters are expected that will tend to be aligned west-southwest to east-northeast with the deeper layer mean flow and this will be suggestive of a threat of repeating/training cells. Rainfall rates are likely to reach up into the 1 to 2 inch/hour range with the stronger/organized convective cells and with some storm totals that may reach up into the 2 to 4+ inch range given concerns for repeating/training cells. The latest NASA SPoRT soil moisture data indicates relatively moist antecedent conditions across portions of the Mid-South and this is suggested as well with USGS data showing locally above normal streamflows. Given this and the environmental support for heavy rainfall, a sizable portion of the Marginal Risk area was upgraded to a Slight Risk with an emphasis on Tennessee where the best overlap of moist soil conditions and heavy rainfall potential overlap. Isolated to scattered instances of flash flooding will be possible across this region. Orrison Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_0_l9823E5QfDreDlE2YcBL5tVSYoBVZjfzgKyMXizVG= b8G_P9q9K6eYfxH8_TWykOTYKIAn3xScP9VAd1078_QN-GA$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_0_l9823E5QfDreDlE2YcBL5tVSYoBVZjfzgKyMXizVG= b8G_P9q9K6eYfxH8_TWykOTYKIAn3xScP9VAd107Ng7uglM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_0_l9823E5QfDreDlE2YcBL5tVSYoBVZjfzgKyMXizVG= b8G_P9q9K6eYfxH8_TWykOTYKIAn3xScP9VAd107X1ny0Xw$=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) .