A cluster of severe thunderstorms moved across portions of eastern Iowa and northern Illinois between 16 and 22 UTC on 18 May 2000 in association with a strong shortwave trough. A combination of bow echo and supercell thunderstorms were observed, which generated numerous reports of large hail, damaging wind, and several weak (F0) tornadoes. All tornadoes were of a non-descending mode, occurred within 15 miles of a quasi-stationary synoptic-scale front, and were associated with both bow echo and supercell storm types.

Evolution of the individual mesocyclones will be reviewed. The potential interactions between the synoptic-scale frontal boundary, bow echo/supercell storm mergers and their relationship to the generation of radar observed non-descending tornadogenesis will be discussed. The importance of meso and stormscale analysis through a variety of data sources, including WSR-88D velocity and spectrum width data, in warning operations will be reviewed.