For a start, you might have a look at which cities had severe weather on the day you are interested in (I know Ottawa had some pretty bad weather on Saturday) as there may have been some diversions. From there, you could compile a list of all flights to that city on the day, and then you could do a flightaware search on each one of those to see which were diverted (flightaware will give you a flightrack for a flight). Lots of tedium in there, but it might yield the info you need. There may be better and easier ways to find out what you want to know, but those are the ideas I have. Good luck.