Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Apr 19 2023 08:27:43 FOUS30 KWBC 190827 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 426 AM EDT Wed Apr 19 2023 Day 1 Valid 12Z Wed Apr 19 2023 - 12Z Thu Apr 20 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE CENTRAL PLAINS TO THE UPPER MISSISSIPPI VALLEY... Elevated convection developed overnight and is persisting this morning across the eastern Dakotas, Iowa and Minnesota where there was decent instability rooted above a strong low level inversion, a mid level shortwave approaching the area, and strong upper level diffluence. Much of this region has wet antecedent conditions, as much as 400 to 600% of normal the past week. Additional showers and thunderstorms are ahead the cold front tracking through eastern portions of the Central Plains before expanding southwest to northeast through the night from eastern Kansas through Wisconsin. Some the stronger instability and lift will be nosing into Kansas and Missouri which favors higher QPF to setup from eastern Kansas through southern Iowa. There is a risk for rainfall rates over 1"/hr per the 12Z HREF. While KS will have the most instability, antecedent conditions are most favorable for flash flooding in Wisconsin due to added snowmelt from the recent winter storm over the western half of the state. Thus if FFG is able to be exceeded, we could realize some lower end flood impacts, especially over any more susceptible areas. The Marginal Risk area already in effect highlights where there is an elevated threat for excessive rainfall. Minor tweaks were made to reflect the latest trends. Campbell Day 2 Valid 12Z Thu Apr 20 2023 - 12Z Fri Apr 21 2023 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FROM NORTHEAST TEXAS TO THE MID-SOUTH... A steady stream of deep-layered moisture will be advecting northward as a cold front progresses southeast form the Central plains. PW values of 1 to 1.75 inches (1.5 to 2 sigma) will in place ahead of the frontal boundary as it approaches the Mid-South and eastern Texas Thursday afternoon. Continued southwesterly deep layer flow, which will be nearly parallel to the front will be conducive for storms repeating with some backbuilding of convection. General consensus depicts areal averages of 1 to 3 inches from eastern Texas to the Mid-Mississippi Valley with amounts closer to the 1 inch mark for the Upper Mississippi Valley and Great Lakes. FFG will remain lower due to recent rains (and snowmelt in the Upper Midwest), thus keeping an elevated threat for flooding concerns. The Slight Risk area was expanded further southwest into eastern Texas and southward into northern Louisiana. The southern bounds of the Marginal Risk ares was also expanded south and eastward to reflect the latest WPC forecast and QPF trends. Campbell Day 3 Valid 12Z Fri Apr 21 2023 - 12Z Sat Apr 22 2023 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FROM THE CENTRAL GULF COAST TO THE MID-SOUTH... The cold front mentioned in the day 2 period will continue to advance into the Deep South and into the Tennessee/Ohio Valley during this period. Meanwhile the deep layered Gulf moisture will continue to fuel showers and thunderstorms ahead of and along the frontal boundary. The strongest moisture convergences will align from southern Louisiana to western Tennessee. Model guidance does show some spread in exactly where the highest QPF will be and of what values. However, most are indicating 2 to 3 inches along the Lower Mississippi Valley with embedded higher amounts along the Gulf Coast. A Slight Risk for excessive rainfall spans for the extreme eastern Texas/Louisiana to western Tennessee/Kentucky border. A broader Marginal Risk spans from Texas to Alabama and then northward to Ohio. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8fi_Kl4bW-HTBYf8CPRkPGnoK1dkceabV5lPeOOVRpYb= jwzJYe5Y3vdesg3EKe8nGQV8rvnoS5kihTiKZRp5Lavb3C0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8fi_Kl4bW-HTBYf8CPRkPGnoK1dkceabV5lPeOOVRpYb= jwzJYe5Y3vdesg3EKe8nGQV8rvnoS5kihTiKZRp5xDYsJ5g$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8fi_Kl4bW-HTBYf8CPRkPGnoK1dkceabV5lPeOOVRpYb= jwzJYe5Y3vdesg3EKe8nGQV8rvnoS5kihTiKZRp5iqgPleg$=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) .