During the overnight hours of the 4th/early on the 5th, thunderstorms developed in Oklahoma...but weakened as they headed into Arkansas. Left behind was a system (and relatively cool air) aloft, or mesoscale convective vortex (MCV). As the MCV headed slowly to the east, it moved over unstable air still present in about the southeast half of the state.

In the picture: A mesoscale convective vortex (MCV) approached areas with CAPE (Convective Available Potential Energy) values approaching 2000 J/kg (in central Arkansas), with thunderstorms forming west of Little Rock (Pulaski County) around 230 pm CDT on 07/05/2005. High CAPE values are often created when relatively cool air aloft moves over warm/moist air near the ground. This setup gives air parcels a lot of lift...with rising parcels (updrafts) feeding developing storms.

During the overnight hours of the 5th/early on the 6th...the MCV turned into a heavy rain maker. Some parts of central Arkansas reported over 4 inches of precipitation. In some spots,  more rain occurred during this event than would normally occur in the whole month of July!
In the picture: Twenty four hour rainfall totals as of 1 pm CDT on 07/06/2005.

Twenty four hour rainfall totals as of 1 pm CDT on the 6th included 4.38 inches at Little Rock (Pulaski County), 3.23 inches at North Little Rock (Pulaski County), an estimated 3.25 inches at Benton (Saline County), and 2.19 inches at Pine Bluff (Jefferson County).