Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 335 PM EDT Fri May 9 2025 Day 3 Valid 12Z Sun May 11 2025 - 12Z Mon May 12 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHEAST... 20Z Update: The primary change for the forecast was a general expansion of the SLGT risk area further northeast into SC to account for the heavier rainfall threat protruding inland given the strong uni-direction component advecting rich Gulf moisture poleward between the closed upper reflection over the Mississippi Valley and the surface ridge over the Western Atlantic. Cold front from the north will also hit a roadblock as it motions south, likely becoming more quasi-stationary across North GA and the SC Piedmont before being pushed back as a warm front. This will likely coincide with a stronger low-level convergence signature up into those areas by the afternoon and beyond on Sunday into Monday. Considering the nature of the persistent moisture advection regime and enhanced theta_E pattern, expecting widespread thunderstorm development with rates likely reaching between 1-3"/hr within the heaviest cores. Antecedent soil conditions should moisten with the day prior, so the overlap will create a better threat for natural runoff, not including the urban threat that is customary in these setups. The previous SLGT risk was maintained with those expansions to reflect the latest trends. Kleebauer ..Previous Discussion.. A wave of upper level energy will pivot around the upper low across the Southeast, sparking another wave of convection from the Gulf Coast to the Southeast Atlantic Coast. Models are showing a more organized area of surface low pressure moving into the Southeast with significant rainfall totals on the eastern side. Widespread totals of 1.5-2.5 inches are expected with locally high amounts above 3 inches. Considering this will be the second day in a row with heavy rainfall in the Southeast, areas with saturated soils from the day before may be slightly more prone to flood impacts with additional heavy rain on Sunday. The most favorable flash flood conditions will be across North Florida and southern and central Georgia where 1000+ J/kg MUCAPE and 30+ knots of effective bulk shear with support organized convection. Additionally, precipitable water values in excess of 1.5 inches will support efficient rain rates in strong thunderstorms. A Marginal Risk area is in effect for much of Alabama, Georgia, South Carolina, and North and Central Florida, with an embedded Slight Risk area over North Florida and southern and central Georgia. Dolan Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt