Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Apr 16 2023 07:42:41 FOUS30 KWBC 160742 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 341 AM EDT Sun Apr 16 2023 Day 1 Valid 01Z Sun Apr 16 2023 - 12Z Sun Apr 16 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE GREAT LAKES...OHIO VALLEY...AND SOUTHEAST FLORIDA... ....Great Lakes... Waves of low pressure are expected to lift northward along an existing stationary boundary across Wisconsin today. Increasing large scale forcing for ascent is expected as the mid/upper level shortwave trough takes on a negative tilt, pivoting the surface low northward and then northwest. The strong ascent coupled with an axis of higher moisture streaming northward wrapping into the system should yield showers and embedded thunderstorms across eastern Wisconsin through the U.P. of Michigan. Guidance shows a few rounds of precipitation through the afternoon, then much colder air begins to wrap into the system with a gradual west to east changeover to mixed precipitation, at least through central Wisconsin. Far eastern Wisconsin into Michigan will remain warm enough through the period to support rain where localized totals of 1-2" will be possible. Some of this rainfall will fall on sensitive ongoing snowmelt areas, particularly for the U.P. of Michigan where flash flood guidance is particularly low and the additional rainfall could lead to or initiate new flooding. ....Ohio Valley... Strong forcing for ascent is expected over the region ahead of the negatively tilted shortwave trough over the Upper Midwest. A progressive front will sweep through the region and with peak heating and modest amounts of moisture, a line or two of stronger thunderstorms will move through with isolated 1"+/hr rain rates possible. While storm motions are likely to be quick enough to limit widespread issues and antecedent conditions are rather dry, the potential exists for a quick/intense period of rainfall over susceptible areas leading to isolated flash flooding. ....Southeast Florida... Deep convection is expected to develop across the Florida Peninsula this afternoon as a embedded shortwave trough currently over the north-central Gulf begins to advance toward the region. An increase in the low level convergence with the approach of the mid level shortwave trough combined with decent instability and moisture should yield several clusters of strong thunderstorms. Intense rain rates approaching 2"/hr will be possible with localized 3"+ totals possible based on the 00Z hi-res guidance and HREF neighborhood probabilities which for 3" approach 50 percent (20 percent for 5"). This intensity and amount of rainfall over a short period could lead to flash flooding over more susceptible/vulnerable locations like urban areas from the Treasure Coast southward through the Miami/Ft. Lauderdale metro. Taylor 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!4wZiKW8umIPtN3hHMmwYpG44dRITaZoEwXL3JlK21BgI= O37-e2WBZE5f_52qlIhI1kg6kVUi7EUZC2smc7uwovpj4hA$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4wZiKW8umIPtN3hHMmwYpG44dRITaZoEwXL3JlK21BgI= O37-e2WBZE5f_52qlIhI1kg6kVUi7EUZC2smc7uwWepLXvQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4wZiKW8umIPtN3hHMmwYpG44dRITaZoEwXL3JlK21BgI= O37-e2WBZE5f_52qlIhI1kg6kVUi7EUZC2smc7uw-WT2YUM$=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) .