Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Feb 06 2023 20:30:52 FOUS30 KWBC 062030 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 330 PM EST Mon Feb 06 2023 Day 1 Valid 16Z Mon Feb 06 2023 - 12Z Tue Feb 07 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann Day 2 Valid 12Z Tue Feb 07 2023 - 12Z Wed Feb 08 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE ARKLATEX AND PORTIONS OF THE SURROUNDING REGION... A positively-titled trough ejecting out of the Four Corners region Tuesday begins to take on a neutral-tilt as it approaches central Texas. At the same time, a jet streak over the Ohio Valley strengthens to near 130 kts by late Tuesday/early Wednesday, providing large-scale forcing for ascent across the ArkLaTex region as it takes on an increasingly anticyclonic arc farther downstream. Deep layer southerly flow ahead of the system will usher higher moisture northward, characterized by precipitable water values in excess of 1.25 inches (between 2 and 2.5 standard deviations above the climatological mean). The favorable overlap of strong lift, high moisture, and sufficient instability (MUCAPE of 1000 J/kg) should produce intense rain rates exceeding 2"/hr at times. In addition, deep layer flow being nearly parallel to expected storm motions could allow for training/repeating rounds of heavy rainfall. The models have been consistent with the forcing in the big-picture for several days now. However...there has been a shift towards the main upper trough to be less progressive than before...which necessitated shifting the Marginal and Slight Risk areas a bit farther westward once again and to trim a small portion of the Marginal Risk area on the northern side of the previously issued areas. The latest NASA SPoRT 0-40 cm relative soil moisture values remain above the 65th percentile of climatology across a good portion of eastern TX (and 7-day precipitation departures are as high as 300-600 percent of normal across much of northern and eastern TX). Bann/Churchill Day 3 Valid 12Z Wed Feb 08 2023 - 12Z Thu Feb 09 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL MAINLY OVER NORTHERN ARKANSAS AND SOUTHERN MISSOURI... Introduced a Slight Risk area that mainly covered northern Arkansas and southern Missouri plus a very small amount of adjoining states now that the models have slowed the forward speed of the main upper system. The result of that was more overlap of QPF on Day 2 and Day 3 with a corresponding increase in rainfall amounts. The overall set up and forcing remained similar...namely deep layer southerly flow entrenched ahead of the trough which increases tropospheric moisture levels across the region with precipitable water values reaching as high as 1.5-1.8 inches. This increase in tropospheric moisture, combined with strong lift and instability (MUCAPE of 500-1000 J/kg), will result in the potential for heavy rainfall with areal average 1-3" amounts (and locally 2.5 to neary 4 inches where there is best overlap with Day 2) expected. The model spread remained higher than usual but there was at least some convergence of solutions compared with runs 24 hours ago. The WPC Excessive Rainfall Outlook has therefore depicted Slight Risk area embedded within a fairly broad Marginal Risk area. With regard to antecedent conditions, NASA SPoRT 0-40 cm relative soil moisture values remain elevated across the Lower Mississippi Valley, whereas these soil moisture values are well below normal across the Middle MS and OH Valleys. Bann/Churchill Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!9UvHY2wYHd8EeDFZ83m5AZxcoQoWXYXHDSJ_ZMQdYWd-= sKHWSpNsidcKgv7vGRIo9zNMwm_N1VYX1B-scc9cwaJIr7M$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9UvHY2wYHd8EeDFZ83m5AZxcoQoWXYXHDSJ_ZMQdYWd-= sKHWSpNsidcKgv7vGRIo9zNMwm_N1VYX1B-scc9cPDt6XwE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9UvHY2wYHd8EeDFZ83m5AZxcoQoWXYXHDSJ_ZMQdYWd-= sKHWSpNsidcKgv7vGRIo9zNMwm_N1VYX1B-scc9cTmYJCJM$=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) .