A catastrophic and potentially historic storm system is targeting the central U.S., prompting multiple weather alerts for severe thunderstorms, tornadoes, and flash flooding. Forecasters have issued a rare level 5 of 5 severe weather threat, warning of long-lived, EF3-plus tornadoes primarily affecting regions across the Midwest and South. Millions are at risk for significant tornadoes and generational flooding. As a once-in-a-generation storm system approaches, communities are bracing for the unpredictable weather pattern forecasted to bring torrential rain, damaging winds, and hail the size of golf balls. Alert days have been declared as experts warn of potential rainfall amounts that could lead to catastrophic flooding, with some areas anticipating the possibility of a 1,000-year flood. Residents in states like Missouri, Illinois, and Tennessee are advised to prepare for severe conditions as storms are expected to continue throughout the week.