Today is the 20th anniversary of the Mayfest storm. This event remains one of the costliest hail storms in history. Hail injured 60 people bad enough to require hospitalization and the storm claimed 20 lives (none to hail - 17 where due to flash flooding). This event forever changed the Integrated Warning System and lead to better partnerships between the NWS and emergency managers.The NWS Ft. Worth WFO has a recap of this event at: http://www.srh.noaa.gov/fwd/?n=mayfest15 A case study was also written on this storm: http://www.srh.noaa.gov/images/fwd/mayfest/Mayfest1995ConfPaper.pdf Here is an excerpt from that study:"The most damaging non-tornadic severe thunderstorm in the United States, and perhaps world history, occurred in the Dallas/Fort Worth Metroplex (DFW) during the late afternoon and evening of 5 May 1995. A high precipitation (HP) supercell (Moller et al. 1990) produced significant severe weather over Parker and Tarrant Counties, including hail varying in size from 4.5 to 11.5 cm, along with winds exceeding 30 m s-1.The supercell struck the Mayfest outdoor festival just south of downtown Fort Worth; 60 people were hospitalized, four critically, from injuries received from very large hail (Storm Data 1995; NOAA 1995). The HP supercell later merged with a bowing squall line over eastern Tarrant County. Extreme rainfall ensued over eastern Tarrant County and much of Dallas County, with portions of northern Dallas receiving rainfall rates approaching 23 cm hr-1. In all this event claimed 20 lives, with 17 fatalities attributable to flash flooding. Hundreds more were injured, and total economic losses approached $2 billion (Moller 2002)."