On 5 May 1995, a high-precipitation supercell struck the Dallas/Fort Worth Metroplex, producing damage exceeding that of any prior thunderstorm event in United States history. This devastating storm produced a large swath of baseball to softball size hail over Fort Worth, injuring over a hundred people at the Mayfest event just south of downtown. This supercell later merged with a squall line over eastern Dallas county, resulting in record flash flooding. In all, the storm claimed the lives of 20 people and injured hundreds, and caused more than two billion dollars of damage.

This event challenged meteorologists with several forecast and warning problems. Computer model guidance did not resolve the mesoscale processes preceding storm initiation. Hourly mesoanalyses of various data sets proved to be invaluable in adjusting model forecasts, thereby refining the severe weather threat area. Warning decisions were based on observed data and trends as the event evolved, rather than on model-derived expectations of severe weather type and organization. Combined with realtime spotter information, these adjustments were crucial in identifying the extreme nature of this event.

Numerical model data, surface and upper air observations, satellite imagery, wind profiler data, and WSR-88D radar data are used to reconstruct the antecedent meteorological conditions of this event. We examine WSR-88D data and interpret the high-precipitation supercell storm morphology and the merger of this supercell with the squall line over eastern Dallas county. Lastly, our analyses of rain gage and WSR-88D precipitation data suggest that the supercell/squall line merger likely influenced the incredible precipitation rates (22.88 cm hr-1) over portions of Dallas county, leading to flash flooding.