Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 29 2023 08:27:27 FOUS30 KWBC 290827 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 426 AM EDT Fri Sep 29 2023 Day 1 Valid 12Z Fri Sep 29 2023 - 12Z Sat Sep 30 2023 ....A MODERATE RISK OF EXCESSIVE RAINFALL IS IN EFFECT OVER PORTIONS OF THE NORTHEAST... ....Mid-Atlantic into Northeast... An upper-level trough will support the amplification of an inverted surface trough and low pressure system off the Mid-Atlantic/Northeast Coasts today. There will be thunderstorms with heavy rainfall and serious flash flooding concerns over parts of the northern Mid-Atlantic and Northeast. Rounds of showers and thunderstorms, which began overnight, will continue and pickup in intensity through the morning rush hour. Some of the 00z hi-res guidance didn't capture the 01z-02z storms that moved into the New York Metro so there is a concern that this under performance may continue into the day 1 period. This antecedent rainfall has also primed surfaces for runoff of subsequent rainfall. A favorable low level jet, shallow instability and substantial surface frontogenesis will combine to produce efficient rainfall rates on the order of 0.25-0.5"/hr from northeastern New Jersey to coastal Connecticut where a Moderate Risk of Flash Flooding is in effect. Anywhere from 2-6" of rainfall are expected to accumulate by later this evening when the greatest threat of flash flooding will subside. Areas that are prone to flash flooding across the New York Metro Area will likely experience flash flooding today, so turn around don't drown! ....Upper Midwest/Great Lakes... Shortwave energy propagating south-north into Canada will drive showers and scattered to isolated thunderstorm activity over the Upper Midwest today. Another inverted surface trough will direct and enhance anomalous moisture plume with PWATs of 1-2" into much of Minnesota and northwestern Wisconsin. Rainfall totals of 1-2 inches are possible over portions the Upper Midwest by tomorrow morning. ....Florida... The back end of a slow moving cold front will act as a focus for scattered to isolated showers and thunderstorms today. A Marginal Risk area was continued to account for any localized flash flooding concerns that may arise. Kebede 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!4mRbtcgIgdLGcE8V-zXl8si-PB9kZvOQhgSTY8uTjyTR= AFb0UZ3yR_3-0Q78yKu_MgOjfWDqqNZM3ZaVJtfes0hvYZs$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4mRbtcgIgdLGcE8V-zXl8si-PB9kZvOQhgSTY8uTjyTR= AFb0UZ3yR_3-0Q78yKu_MgOjfWDqqNZM3ZaVJtfeYoK0Lpc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4mRbtcgIgdLGcE8V-zXl8si-PB9kZvOQhgSTY8uTjyTR= AFb0UZ3yR_3-0Q78yKu_MgOjfWDqqNZM3ZaVJtfehnwexM4$=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) .