Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Dec 06 2022 23:33:01 FOUS30 KWBC 062332 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 632 PM EST Tue Dec 06 2022 Day 1 Valid 01Z Wed Dec 07 2022 - 12Z Wed Dec 07 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF KENTUCKY AND TENNESSEE... Locally heavy rainfall is possible through tonight across portions of the Lower Ohio Valley and Tennessee Valley and may result in isolated instances of flash flooding. The latest water vapor imagery shows an embedded shortwave trough moving through Arkansas while at the surface, the latest analysis shows a warm front slowly advancing northward through Kentucky. Showers and thunderstorms are expected to increase in coverage over the next several hours as an increase in the low level jet (30-35 kts at 850 mb) surges precipitable water values above 1.5" and elevated instability of around 500 J/kg is present. With the mean flow out of the southwest oriented parallel to the expected storm motions, repeating rounds of convection are likely, initially across western to central Kentucky then southward across western to middle Tennessee as a cold front slips southward through the region. The most recent runs of the HRRR have shown an uptick in the potential for locally heavy rainfall with 1-1.5" hourly totals at times and localized 2-2.5" totals possible through 12Z Wednesday. These types of rates are borderline based on the most recent flash flood guidance, and NASA SPoRT soil moisture percentiles show fairly dry soils. The rainfall may end up being more beneficial but there's a low probability of isolated flash flooding based on the rates and potential training, so a Marginal Risk was introduced. Taylor Day 2 Valid 12Z Wed Dec 07 2022 - 12Z Thu Dec 08 2022 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF EASTERN OKLAHOMA INTO NORTHERN ARKANSAS AND SOUTHERN MISSOURI... ....North Texas and Eastern Oklahoma eastward into the western Tennessee Valley... Models still suggest the potential for locally heavy to excessive rainfall from eastern Oklahoma into northern Arkansas and southern Missouri on Wednesday as a southern stream trough pivots across the Southwest U.S. on Wednesday and across the High Plains Wednesday night. As this occurs, the downstream upper level ridging underneath the broad/deep low centered over north-central Canada will result in upper level confluence and an eventual jet streak across the Central Plains and Upper Midwest on Day 2. Increasing southern-stream forcing coupled with the frontogenetic, entrance-region upper jet forcing from the northern stream will make for a favorable environment for deep layer lift across the outlook areas. Both the GEFS and SREF showed a relatively quick bout of robust low-mid layer moisture transport, with 8500-700 mb moisture flux anomalies topping out between +3-3.5. PW values and a stripe of 1.5-1.7" PWs traversing the outlook areas Wednesday and Wednesday night. The progressive nature of the favorable forcing (forward-propagating Corfidi or MBE vectors), along with the relative lack of deep-layer instability (MUCAPEs generally less than 750 J/Kg) will be the primary inhibitors to the flash flood risk. In addition, per the latest NASA SPoRT analysis, 0-100cm soil moisture percentiles are running between 10-30% of normal across much of the outlook area. Nevertheless, per earlier collaboration with WFOs in the Plains and given the anomalous degree of deep-layer forcing and moisture, consistent with the 00Z and 12Z GEFS-based first-guess fields, maintained the targeted Slight Risk area and surrounding Marginal Risk areas with few changes. Hurley/Bann Day 3 Valid 12Z Thu Dec 08 2022 - 12Z Fri Dec 09 2022 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!58m91nZjEnKy3saxI4AZd16aIPXcZIuEsENUQVawSqa-= tOfKEKfy5wIjzFoze7BCT_DN3RGxTSTe_DCggqNJYLAHzSk$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!58m91nZjEnKy3saxI4AZd16aIPXcZIuEsENUQVawSqa-= tOfKEKfy5wIjzFoze7BCT_DN3RGxTSTe_DCggqNJZorG0gs$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!58m91nZjEnKy3saxI4AZd16aIPXcZIuEsENUQVawSqa-= tOfKEKfy5wIjzFoze7BCT_DN3RGxTSTe_DCggqNJVrMvZUQ$=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) .