From Westjet: A winter storm warning has been announced for Ottawa, Quebec City and Montreal on Thursday, December 27th.
This may cause the delay or cancellation of WestJet flights to and from Ottawa, Quebec City and Montreal. We advise all guests travelling to or from these areas on Thursday, December 27th to check the status of their flight prior to leaving for the airport.
From AC: Cities impacted: Cleveland, Montreal, Ottawa, Quebec City, Toronto.
Read more: http://www.aircanada.com/en/travelinfo/before/operation/index.html