The image below represents an EWR radar picture of the August 20, 2009 storm line that spawned the tornados that hit the town of Vaughan north of Toronto, the town of Durham, and areas of Milton. In Vaughan, as many as 180 homes were damaged, some beyond repair. In Durham, a 12 year old child was killed by debris.

EWR tracked a pair of mesocyclones (not visible in this animation) over the Vaughan area, and a confluence of cells over the Milton area the evening of the storms.

Update 2009/08/24: Animation fixed. The first thumbnail below is the animation tracking the storm line across southern Ontario. The second thumbnail is the smoothed Base Reflectivity scan of the line at the time of peak activity over Vaughan (7:03 PM 2303 UTC).

Unfortunately, I only collected the Base Reflectivity data at the time, not expecting the outcome to be as significant. The animation consists of over a 100 individual radar frames, each of which is available as a separate image.