Extreme February Precipitation and Historic Flooding across Northern Indiana and Southwest Lower Michigan

A combination of unusual and record meteorological conditions led to an extreme precipitation event and historic flooding across much of northern Indiana and southwest Lower Michigan during February 2018. The month began as the snowiest on record as observed by the South Bend Indiana cooperative snowfall observer. Nearly 30 inches of snow fell in just over 2 weeks with a maximum snow depth reaching 15 inches and a liquid content between 1 and 2 inches. This snowfall would melt over the following week as temperatures slowly warmed. A strong low pressure system would then usher in anomalous precipitable water values over 400 percent of normal and several rounds of heavy rainfall between February 19th and 21st. Rainfall amounts over this 3-day period exceeded 6 inches across a large part of the region, more than three times the monthly normal. The combination of melting snow and heavy rainfall set the stage for historic flooding that followed with many rivers reaching record crests and a few exceeding previous record crests by nearly 2 feet. Homes, businesses and roads were flooded for days and several roads were washed out entirely. A disaster declaration was issued for 9 counties across northern Indiana by the Governor of Indiana while federal disaster assistance was approved by the President of the United States for 5 northern Indiana counties.

This presentation will discuss the synoptic and mesoscale meteorological conditions that contributed to the development of extreme February rainfall as well as the antecedent and hydrological factors that led to the devastating flooding. The National Oceanic and Atmospheric Administration (NOAA) Atlas 14 Precipitation Frequency Tables will be shown to put the rainfall event into a historical perspective. Impacts to local communities and infrastructure as well as lessons learned from a local after action review will be discussed.