A cold front approached the region from the west, preceded by a squall line. The airmass that entered western Louisiana on May 8 exhibited considerably lower dewpoints than the tropical airmass across east Louisiana and southeast Mississippi. By the evening of May 9, the cold front dissipated in the vicinity of Baton Rouge. The remains of the front served as a focusing axis for heavy precipitation that continued into the late morning hours of May 10. An upper-level trough helped to provide upper-level support to the system. At the surface, warm and moist air moved in from the Gulf of Mexico continually during the event. The swath of highest rainfall totals was closely tied to a theta-e ridge at the 850 mb pressure surface, which stretched from the central Gulf of Mexico into the Mississippi River Delta area.
