Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 13 2025 15:51:39 FOUS30 KWBC 131550 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1150 AM EDT Thu Mar 13 2025 Day 1 Valid 16Z Thu Mar 13 2025 - 12Z Fri Mar 14 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS=20 OF SOUTHERN CALIFORNIA... The prior Slight Risk for the region has been reduced to a=20 Marginal Risk given that the more widespread convection with=20 heavier rates associated with the cold front pushing inland through southern California will shortly clear the vicinity. However, due=20 to the chance of a few lingering storms and potential for the=20 redevelopment of a few post frontal showers on top of any standing=20 or overflow water in poor drainage/urban areas, have maintained a=20 Marginal Risk through this afternoon. Putnam Day 2 Valid 12Z Fri Mar 14 2025 - 12Z Sat Mar 15 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE LOWER TO MID MISSISSIPPI VALLEY INTO PARTS OF THE OHIO AND TENNESSEE VALLEYS... A strong mid-to-upper level shortwave crossing the Southwest on Day 1 is expected to move east of the Rockies, with a negatively-tilted low developing over the central Plains early in the period. Powerful forcing is forecast to interact with what is expected to be a relatively modest plume of moisture advecting north ahead of the system. Storms are forecast to develop initially over the lower to mid Mississippi Valley Friday afternoon before moving east into the Tennessee and Ohio valleys during the evening and overnight. Cell motions will likely be quite progressive given the very strong wind fields in place. Therefore, this convection will likely pose more of a severe risk than a flash flood threat. However, given the strong dynamics, along with sufficient instability for deep convection, expect that rainfall rates will be briefly intense enough to produce localized amounts that exceed current model forecasts (maybe locally over 2 inches). Still, this appears to be a lower-end flood threat, and probably confined to localized impacts over more sensitive urban or low lying areas that are impacted by a quick burst of intense rainfall. Pereira Day 3 Valid 12Z Sat Mar 15 2025 - 12Z Sun Mar 16 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE TENNESSEE AND OHIO VALLEYS... Even as the previously noted low lifts to the north through the Great Lakes into Ontario, the upper pattern will remain amplified across the central U.S. as an upstream shortwave dives southeast into the southern Plains on Saturday. A surface wave developing along the leading system's trailing cold front will help focus deeper moisture tapped by strengthening southerly winds. While differences in the details remain, the general consensus of the 00Z guidance indicates that widespread accumulations of 2-4 inches centered over parts of the Tennessee and lower Ohio Valleys are likely. A large Slight Risk was maintained across the region, reflecting the higher probabilities for 2 inches or more shown by by the GEFS/ECENS and where deeper moisture, interacting with strong forcing, along a relatively slow moving front, is expected to raise the potential for heavy amounts late Saturday into early Sunday. This remains a higher-end Slight Risk for parts of the area, with an upgrade to a Moderate Risk possibly forthcoming, especially once the period moves within the hi-res window and details concerning rainfall rates and the placement of the heaviest amounts become more clear. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8tAAChe0WtvHrDy4liYmKRZnDpT-h3pYGZsf6M4SpFWj= UJUdtU6SSh_T9BNA1ZVaFLk6vsWNaZH8Ayg3y0ZzpDYmRFs$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8tAAChe0WtvHrDy4liYmKRZnDpT-h3pYGZsf6M4SpFWj= UJUdtU6SSh_T9BNA1ZVaFLk6vsWNaZH8Ayg3y0ZzGvo6ejc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8tAAChe0WtvHrDy4liYmKRZnDpT-h3pYGZsf6M4SpFWj= UJUdtU6SSh_T9BNA1ZVaFLk6vsWNaZH8Ayg3y0ZzkSpm81c$=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .