User blog comment:Jarrell Tornado/July 31, 1987 - Edmonton's "Black Friday"/@comment-26014793-20170802044242

It's always been my opinion that the Edmonton tornado's rating should have been upgraded to F5, although Environment Canada is famously very conservative with tornado ratings. It's true that no houses were swept away, but in all likelihood that was because the tornado was at its peak strength in industrial areas where there were no houses at all. The long-distance tossing of multi-ton oil tanks is similar to damage from several previous F5 tornadoes (Prague, Oklahoma; Lubbock, Texas; Niles, Ohio) and steel beams at the lumber plant were twisted and mangled, similar to the Parkersburg, Iowa EF5. There's also the issue of wind-rowing of debris and partial scouring of grass, both of which are unusual in E/F4 tornadoes but common in E/F5 tornadoes.