Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 325 AM EST Thu Dec 4 2025 Day 1 Valid 12Z Thu Dec 04 2025 - 12Z Fri Dec 05 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL GULF COAST... Upglide/warm-advective elevated convective activity is ongoing this morning across portions of the central Gulf Coast with localized hourly totals topping out near an inch or so (per MRMS estimates). Right entrance ascent to 150-170 kt jet centered over the Ohio Valley will keep isentropic moisture flux across the surface front that will remain oriented along and south of the coast. A weak mid-level shortwave will slide from west to east along the southern periphery of the jet streak maintaining 20-25kt of west- southwesterly 850mb flow which given ~1.75" PWs and the potential for lingering marginal instability (MU CAPE up to 1000 J/kg now, but forecast to decrease below 500 J/kg later this morning) may maintain elevated convective development into midday. Internal training of back-building convective elements will present the greatest potential for higher rainfall totals across the Bayous of south-central LA. Hi-Res CAMs are in general good agreement with the heaviest rainfall along and south of I-10 (where 3" exceedance probs from both the 00z HREF and experimental REFS are contained). Little change in the inherited MRGL risk, which will likely be pulled around midday as convective activity wraps up. Churchill/Gallina Day 2 Valid 12Z Fri Dec 05 2025 - 12Z Sat Dec 06 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Churchill Day 3 Valid 12Z Sat Dec 06 2025 - 12Z Sun Dec 07 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL GULF COAST THROUGH NORTHERN FLORIDA/SOUTHERN GEORGIA AND FAR SOUTHERN SOUTH CAROLINA... A quasi-stationary front draped near the FL Panhandle may become convectively active by Day 3 (particularly late Saturday night into Sunday morning) with the potential for localized training along the boundary with nearly unidirectional westerly flow aloft. Maintained an inherited MRGL risk with instability being the primary limiting factor, but both global ensembles (GEFS and ECENS) suggest decent odds of 2" exceedance (which may translate to localized totals as high as 3-4" with the addition of CAMs in the coming days). Churchill Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt