22 May 2004 brought a highly expected outbreak of severe weather, including over 50 tornadoes, to southern Nebraska and western and central Iowa. During this outbreak, a tornado touched down just west of Daykin, Nebraska, and would continue to track northeast for 52 miles, eventually meriting an F4 rating. The tornado reached its overwhelming maximum width of 2.5 miles around Hallam, Nebraska; it resulted in 37 injuries and one fatality. As the threat for such an explosive condition was pointed out fairly well in advance, this presentation focuses on what made this situation so identifiable as a dangerous one. Numerous factors in the surrounding synoptic and mesoscale environment are considered, with particular emphasis placed on the RUC sounding-derived parameters.

Additionally, multiple supercells formed that evening; only one, however, produced the intense, long-track Hallam tornado. Another supercell tracked across south-central Nebraska, generating at least six weaker, short-track tornadoes from Furnas to Clay County. At times this supercell was separated from the Hallam supercell by less than a hundred miles. The differences in the convective mesoscale environments of the two supercells are examined in an attempt to infer why one produced such a more powerful outcome.