National Weather Service forecasts and ensemble model guidance indicate the highest probabilities of measurable precipitation on September 12 across the eastern and central United States, driven by a frontal boundary and associated moisture plume with precipitable water values above the 90th climatological percentile. Scattered to numerous showers and thunderstorms are expected from the Mid-Atlantic and Ohio Valley southward into the Southeast and Gulf Coast, with lower chances in the northern Plains and minimal risk in the Southwest and West Coast under drier high-pressure influence. Recent NWS excessive rainfall discussions highlight slight risks in portions of the Ohio Valley and Mid-Atlantic, where local rates could exceed 1 inch per hour. Updated model runs and 24-hour probability of precipitation products from the Weather Prediction Center will provide the next key inputs for traders assessing regional resolution thresholds.