Record rainfall fell across much of the St. Louis metro area early Tuesday morning, a recipe for disaster during the morning rush hour. More than 10 inches of rain fell in the span of twelve hours, with isolated one-foot amounts in parts of St. Charles County. Considering the many highways and the urban environment, the drainage capacity was poor with the excessive rainfall rates.
Even in Mid-Missouri, rainfall totals exceeded 6 inches in parts of Audrain and Montgomery counties Tuesday morning, shutting down some roads until Tuesday evening.
The weather pattern was ideal for an axis of heavy rain and training thunderstorms to continue to develop over the same areas. With a frontal boundary serving as a focal point for storms to the south, a strong low-level jet stream from the southwest to push moisture, and a strong upper-level jet stream to boost lift, all the ingredients come together. are brought together quickly. .
The heavy rain axis was just north of I-70, extending southeast into St. Charles and St. Louis counties. Water levels quickly rose on highways, stranding drivers trying to get to work and forcing residents and employees to evacuate their homes and businesses.
A new daily rainfall record was set at Lambert St. Louis Airport, where the midnight-to-midnight rainfall total was 8.64″. This broke the previous record of 6.85″, set in 1915. when the remnants of the Galveston hurricane brought heavy rains to St . Louis. The storm event total in St. Louis was 9.07″ for Tuesday.
Three of the five wettest years in St. Louis have all occurred in the past two decades. You may remember the devastating winter floods of 2015 that shut down highways in St. Louis in December. 61.24″ of rain was recorded that year.
The second wettest year on record was 2008, when much of the Midwest experienced significant riverine flooding. In 1982, St. Louis recorded nearly 55 inches of rain; a year that saw more flooding in December with 9 to 13 inches recorded at the start of that month.
The rains that led to the great flood of 1993 gave an annual reading of 54.76″, making it the 4th wettest year in St. Louis. More recently, heavy snowfalls and spring rains have caused flooding in 2019, the fifth wettest year on record.