National Weather Service forecasts as of September 20 highlight a marginal risk of excessive rainfall on September 21 across the Mid-Atlantic and parts of New Mexico, driven by a lingering frontal boundary interacting with moist, unstable air masses. Scattered showers and thunderstorms are expected in the Southeast and Florida, where afternoon heating will boost convective activity, while the Northeast sees clearing skies and lower precipitation chances following heavy rain on the 20th. Model consensus from the Weather Prediction Center shows steering patterns favoring localized downpours rather than widespread systems, with resolution likely hinging on official 24-hour rainfall reports from NOAA stations. Updated short-range model runs and excessive rainfall outlooks expected later today could refine these probabilities for traders.