Insider Blog: Tuesday’s perfect recipe for historic flooding in St. Louis
Record-setting rainfall fell across much of the St. Louis metro area on early Tuesday morning, a recipe for disaster during the morning rush hour. More than 10 inches of rain fell in a matter of twelve hours, with some isolated amounts of a foot in parts of St. Charles County. Given the many highways and urban environment, drainage capability 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, closing some roads through Tuesday evening.
The meteorological setup was ideal for an axis of heavy rain and training storms to keep developing over the same areas. With a frontal boundary to serve as a focal point for storms to our south, a strong low level jet stream coming in from the southwest to push in moisture, and a strong upper level jet stream to reinforce lift, all of the ingredients came together quickly.
The axis of heavy rain 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-midnight rain total was 8.64". That broke the previous record of 6.85", set back in 1915 when the remnants of the Galveston Hurricane brought heavy rain to St. Louis. The storm event total in St. Louis was 9.07" for Tuesday.
Three of the top five wettest years in St. Louis all happened in the last two decades. You might remember the devastating flooding in the winter of 2015 that shut down interstates 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 river flooding. In 1982, St. Louis recorded almost 55" of rain; a year that was marked by more December flooding with 9-13 inches recorded early that month.
Rains that resulted in the Great Flood of 1993 gave an annual reading of 54.76", making that the 4th wettest year in St. Louis. More recently, significant snowfall and rounds of spring rain caused flooding in 2019, the fifth wettest year on record.
