This type of thing happens quite often. If the weather is anticipated well in advance flow will implement a ground delay program on the 33's but if the winds swing quickly and force ATC into an unforseen or early 33 operation they are caught with their pants down and must use a ground stop in order to just be able to catch up with the already airborne inbound flights. You can look up present and past ATC/airport issues here: www.fly.faa.gov/adv/advAdvisoryForm.jsp
including Canadian ones.
Normally when a ground stop has ended a ground delay program will be in effect so that all the aircraft that have been delayed do not all leave at once and create another huge mess for ATC. The departure or 'flow times' are requested by carriers and then issued by the flow department. Since a Dash 8 from Timmins carrying 30-50 people takes one of ACA's landing slots at YYZ as does a B767 from YUL with over 200+ people you can see why a Jazz flight would be pushed further back from YTS.