Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 21 2023 08:16:28 FOUS30 KWBC 210816 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 415 AM EDT Sun May 21 2023 Day 1 Valid 12Z Sun May 21 2023 - 12Z Mon May 22 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTH-CENTRAL ROCKIES & HIGH PLAINS, THE NORTHERN ROCKIES, AND THE SOUTHEAST... ....Northern Rockies... Very little has changed in this region with the 00Z suite of guidance. A slowly digging neutral to slightly negatively tilted trough will track east from the Pacific, moving onshore of the coast of WA late this afternoon, then continuing to push inland through tonight. Shower and thunderstorm activity will break out over the Marginal risk area as early as early afternoon per the CAMs guidance, but the stronger storms are expected to hold off until the late afternoon/early evening along the OR/ID border, then track northeast across ID and into western MT. Expect at least 2 rounds of storms to be following this northeastward-oriented conveyor belt that develops ahead of the strong trough. The storms may weaken some with nightfall, but are likely to persist through the overnight tonight across far northern ID and northwestern MT. Wet soil conditions remain in place from recent showers and storms in this area, and while the individual cells will be rather rapid-moving, the multiple rounds of storms interacting with the terrain will make isolated flash flooding a possibility, especially over burn scars, canyons, and other poor-drainage areas. ....South-Central Rockies and High Plains... A rather weak but still significant upper level disturbance crossing through CO today will tap into a bit of Gulf moisture riding a 25 kt southerly LLJ tracking up the TX & OK Panhandles on north into KS. Showers and thunderstorms will develop as early as midday today across CO and NM, and that convection will organize a bit as they encounter the LLJ over the High Plains late this afternoon through this evening. There is some potential for training, but the primary threat is slow-moving storms. Finally soils in this area remain saturated, and will have little to no opportunity to do much drying out over the next few days as repeating lines of storms move through. The dry line will play a role not just today but for the next several days in the development of the strong storms. Localized flooding concerns persist, and the Marginal Risk remains from west-central TX through west-central KS. ....Coastal Southeast... A slow moving front approaching from the north and west will team up with the sea breeze fronts to result in a line of showers and thunderstorms that will be nearly stationary across much of the FL Peninsula and up into GA. The Marginal Risk highlights the the areas where the strongest storms are expected, namely along the front in GA and far north FL, and any sea breeze convection in the northern FL Peninsula through Orlando and possibly Tampa. With wet soils already in place, any storms that form over urbanized or other poor drainage areas will be strong enough given the ample moisture in the area to produce isolated flash flooding. Wegman Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4ZFehrwj_YJCgftHbD0OLj4FXsPtGpm3uSblPWv6Ua6b= sEINERk3LdLOufsMGFJTzvpIEeRMx_QDe8XmjxOOjEM9JYo$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4ZFehrwj_YJCgftHbD0OLj4FXsPtGpm3uSblPWv6Ua6b= sEINERk3LdLOufsMGFJTzvpIEeRMx_QDe8XmjxOO05KuNpY$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4ZFehrwj_YJCgftHbD0OLj4FXsPtGpm3uSblPWv6Ua6b= sEINERk3LdLOufsMGFJTzvpIEeRMx_QDe8XmjxOOCISfFbA$=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) .