Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Sep 01 2025 16:00:46 FOUS30 KWBC 011600 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1200 PM EDT Mon Sep 1 2025 Day 1 Valid 16Z Mon Sep 01 2025 - 12Z Tue Sep 02 2025 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHWEST, TEXAS, CENTRAL PLAINS, TENNESSEE VALLEY, AND EAST=20 COAST OF FLORIDA... Monsoonal moisture persists from southern Arizona through central=20 New Mexico with diurnally terrain driven activity expected with an isolated flash flood risk. The Marginal Risk is maintained with some more of the Mogollon Rim in AZ added. Slowly south-moving frontal zone and abundant Gulf moisture persists over south-central Texas. 2 to 2.4" PW along this zone is 2 sigma above normal and will result in further heavy thunderstorms with at least some organization to redevelop today and last into tonight. This is generally south of the areas impacted with heavy rain yesterday except around the Houston metro. The Marginal Risk is trimmed a bit from the north given the front location. MCV over far southeast Nebraska will continue shifting east through midday with heavy rain to sweep through the KC metro. Further development to the west over eastern Neb/KS is expected later this afternoon. Trimmed the Marginal Risk on the north side where rain has become more stratiform (including over Omaha).=20 Slow-moving convection is developing over the northern TN Valley which is on the southern end of an upper low centered over the OH Valley. This activity should continue to develop and shift south/southwest today over middle TN into northern AL. Marginal Risk is maintained. Easterly onshore flow into Florida from a low located along the same frontal zone that extends to Texas will allow for focused=20 heavy rain south of Jacksonville again, though the risk extends to Miami today, so the Marginal Risk is maintained for the eastern=20 coastal areas. Jackson Day 2 Valid 12Z Tue Sep 02 2025 - 12Z Wed Sep 03 2025 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDDLE TENNESSEE VALLEY... Remnant convection from the overnight period on Monday night will persist into Tuesday as a reinforcing shortwave digs southward and reaches Middle Tennessee by Tuesday night. A weak, but still significant low level jet will advect Gulf moisture northeastward across the Deep South and into Tennessee on Tuesday, which will keep a steady supply of fuel in place for any convection. Thus, expect a long-duration rain event, that while much of it will be light, the LLJ advecting moisture into Tennessee and various different sources of forcing will support some storms becoming strong and able to produce heavy rain. The storms will also be slow-moving, which will lengthen the amount of time any area sees heavy rain. A Slight remains in effect for portions of Mississippi, Alabama, and Tennessee. A cold front will drop into the Northern Plains and Upper Midwest ahead of the strong reinforcing upper trough. Convection is expected fire up along and ahead of the frontal boundary, with potential for heavy rainfall. A Marginal Risk area is in effect for the eastern Dakotas, northern Iowa, Minnesota, northern Wisconsin, and portions of the UP of Michigan. The stalled out front across Florida will support more widespread convection Tuesday afternoon across much of the Peninsula, while the Panhandle dries out a bit from prior days' rains. A second shortwave and associated front will produce areas of heavy rain across portions of the upper Midwest. A Marginal Risk remains in effect for most of central and southern portions of the Peninsula. Monsoonal moisture is forecast to flow into the southwestern U.S. underneath the mean upper ridge notably shifted a bit westward for this period. Scattered convection expected across the region and is covered by a Marginal Risk spanning from eastern California, Arizona, New Mexico and into southern Colorado. Campbell/Wegman Day 3 Valid 12Z Wed Sep 03 2025 - 12Z Thu Sep 04 2025 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PARTS OF THE SOUTHWEST, FLORIDA, AND THE UPPER GREAT LAKES/UPPER MIDWEST... Deep moisture along the stalled frontal boundary will continue to generate convection capable of producing heavy rain across the Florida Peninsula. A Marginal Risk is in effect for most of central and southern portions of the state. Meanwhile, monsoonal moisture and diurnal heating will continue to trigger convection across the West/Southwest maintaining an elevated threat for isolated flash flooding for vulnerable locations. A Marginal Risk is in effect from New Mexico to eastern California. Further north, heavy rainfall is expected across portions of the Upper Midwest/Upper Great Lakes as the frontal boundary continues to advance eastward. A Marginal Risk encompasses portions of Wisconsin and northern Michigan. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-fE0gX9oCqFrbNfY4GTWhM8k6DrLAr3J2tscHvVv-sxL= y-pzHRCVNj-ozfTzZH6SQLPZQcClSZA0xS_obWptHD-d7Vw$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-fE0gX9oCqFrbNfY4GTWhM8k6DrLAr3J2tscHvVv-sxL= y-pzHRCVNj-ozfTzZH6SQLPZQcClSZA0xS_obWptmgtZ308$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-fE0gX9oCqFrbNfY4GTWhM8k6DrLAr3J2tscHvVv-sxL= y-pzHRCVNj-ozfTzZH6SQLPZQcClSZA0xS_obWptNm2pkvM$=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .