Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Dec 14 2022 19:15:24 FOUS30 KWBC 141915 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 214 PM EST Wed Dec 14 2022 Day 1 Valid 16Z Wed Dec 14 2022 - 12Z Thu Dec 15 2022 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM PARTS OF EASTERN LOUISIANA TO WESTERN ALABAMA... 16Z update... An MCS over the south-central U.S. has yielded periods of moderate to heavy rainfall already this morning. A segment of the organized line, particularly from southern Louisiana to eastern Mississippi, have been been training/repeating storms for several hours now and this is expected to persist through the afternoon hours. The latest CAMs still show rainfall rates of 1 to 2.5 inches/hour over this narrow corridor through ~20Z to 00Z December 15 before advancing eastward at a faster pace. The 3-hr FFG have already lowered to 1.5 inches within the Moderate area (Louisiana to western Alabama) and as low as 0.25 inch along the southeast Arkansas/western Mississippi border that is in the Marginal Risk area. Given the the latest observations and model trends, the western edge of the Marginal and Slight Risk areas were adjusted a small amount westward. The Moderate Risk area remained in good order and reflected where the great threat will likely be for the remainder of the period. Campbell The robust upper level jet streak and associated pivoting shortwave energy will cause the broad mid-upper level trough to become more negatively tilted Wed-Wed night, which will result in a slower, more north-south oriented cold front. This will allow for a much slower west to east progression of pre-frontal lines of convection, thereby boosting the chances of 1.5-2.5 inch/hr rainfall rates within the Moderate Risk area per the latest 40km HREF neighborhood probabilities. Once again, the high-res/CAM consensus shows multiple axes of 3-6+ inches within the Moderate Risk area, with isolated maxima of 6-8". Based on the simulated reflectivity guidance, the bulk of these totals will fall within 6 hours, which is supported by the higher (30-50%) HREF probabilities of 6 hourly QPF exceeding 3". Robust low-mid level moisture transport is again depicted with the 00Z guidance, as both the GEFS and SREF indicate 850-700 mb moisture flux anomalies between 3 and 4 standard deviations above normal. The Moderate Risk was largely maintained (lifted north a tad based on the guidance trends) over portions of southern/eastern Louisiana, southern-central Mississippi, and western Alabama given the most favorable environment for sustained, slow moving convection (MUCAPEs 1000-2000 J/kg) and enhanced moisture supply. The Marginal and Slight Risk areas were expanded further north to reflect the latest WPC QPF and latest trends. Hurley Day 2 Valid 12Z Thu Dec 15 2022 - 12Z Fri Dec 16 2022 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 3 Valid 12Z Fri Dec 16 2022 - 12Z Sat Dec 17 2022 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!53n-To80eIDgo0HoaEwxcCD22h6D8rYGhpByn6cICHy-= AlnhsbGw3Qzf32dh0r5b6N5p1UBLF03p74PDjW0OcC34Q8s$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!53n-To80eIDgo0HoaEwxcCD22h6D8rYGhpByn6cICHy-= AlnhsbGw3Qzf32dh0r5b6N5p1UBLF03p74PDjW0OZImftik$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!53n-To80eIDgo0HoaEwxcCD22h6D8rYGhpByn6cICHy-= AlnhsbGw3Qzf32dh0r5b6N5p1UBLF03p74PDjW0OD16neCQ$=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) .