Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 08 2023 08:28:52 FOUS30 KWBC 080828 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 428 AM EDT Fri Sep 08 2023 Day 1 Valid 12Z Fri Sep 08 2023 - 12Z Sat Sep 09 2023 ....A MARGINAL RISK OF EXCESSIVE RAINFALL IS IN EFFECT FOR MUCH OF THE APPALACHIANS, THE I-95 CORRIDOR FROM DC TO NYC, AS WELL AS EAST-CENTRAL FLORIDA... ....Appalachians Through Southern New England... A digging and increasingly-negatively-tilted trough will move over the OH and TN Valleys today. Meanwhile, deep southerly flow will advect tropical moisture northward up the I-95 corridor. This pattern will increase divergence aloft, allowing storms taking advantage of the abundant moisture to organize and train along the Appalachians. Thus, a marginal flash flooding threat exists for much of the Appalachians, Mid-Atlantic, and into southern New England. The axis of heaviest rainfall is likely along and in the immediate eastern foothills of the Appalachians. The Marginal Risk area was expanded eastward to include the I-95 corridor from DC to NYC. In addition to a small eastward shift in the guidance of the heaviest rainfall, the inherent lower FFGs in the cities will allow even the isolated to widely scattered storms to be capable of 1 to 2 inch per hour rainfall rates, causing isolated flash flooding. For the southern Appalachians, rainfall from storms yesterday (Thursday) caused isolated flash flooding in the Roanoke Valley. With potential for similar coverage of storms again today, the Marginal Risk area was expanded to include more of southwest VA and northwest NC. ....East-Central Florida... Sea breeze convergence will initiate a round of heavy thunderstorms within a narrow corridor near the Melbourne area this afternoon. Hi-res deterministic has been consistent over the past succession of runs for a line of 2-3"/hr rainfall rates to run along the eastern FL coast within the more urbanized corridor extending from Melbourne to up near Daytona beach. There will be a little more enhancement in the upper-levels thanks to a digging shortwave trough forecast to the enter the area, providing a bit more ascent compared to the typical mesoscale boundary convergence. This will lead to additional coverage of storms over the central part of the state, including the Orlando metro. The Marginal Risk area was expanded westward to include potential for isolated flash flooding from very efficient rain-making storms, especially in urban areas. 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!9QrwXhFJvBamO2klRxLh08uHsAP7rcIgi9ElezlgIP1E= dVWW3ZkkXMRcJMyVjuSlq4mfrYjbmKlKVK522r2rRiGvJHA$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9QrwXhFJvBamO2klRxLh08uHsAP7rcIgi9ElezlgIP1E= dVWW3ZkkXMRcJMyVjuSlq4mfrYjbmKlKVK522r2rrFpoKKQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9QrwXhFJvBamO2klRxLh08uHsAP7rcIgi9ElezlgIP1E= dVWW3ZkkXMRcJMyVjuSlq4mfrYjbmKlKVK522r2r6GeK41Q$=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) .