Active upper-level low pressure and tropical moisture influx are driving scattered showers and thunderstorms across the southern mid-Atlantic, Ohio Valley, Appalachians, and Florida on September 23, 2026, with National Weather Service and Weather Prediction Center outlooks showing moderate excessive rainfall risk in parts of New Mexico and the mid-Atlantic. An influx of Gulf and Pacific moisture is fueling convective activity from the Southwest into the central Plains, raising flash flood potential where soils are already saturated. In contrast, much of the western U.S. and northern Plains remain dry under high pressure. Official NWS forecasts indicate highest probabilities in coastal Southeast and Four Corners regions, with resolution tied to verified 24-hour precipitation totals from NWS reporting stations. Updated model guidance through the day could refine localized intensity.