Starting Saturday afternoon/evening in a line of precipitation start from southern to eastern Ontario coinciding with a frontal boundary. Overnight Saturday, the storm will ride up this boundary with the heaviest precip in the Ottawa area will be predawn Sunday but will continue throughout the day. The biggest question will be the type of precipitation. It will start out as snow but as the temperature boundaries move around, it may become ice pellets and/or freezing rain. I don't think we will get to straight rain as no model is putting surface temps above 0C. The warm air coming from the south is pushing up against a dome of cold air to our NW. So lower level temps will be colder than upper levels until after the storm passes. If the upper levels can get cold enough, then the precip will be snow and not ice.
Here is A/W's snow map. I have no major issues with it. However, it favours the GFS/NAM solution. Snowfall amounts will significantly depend on the mix of precip.. The Euro is further south with the amounts. Yes, I am still rooting for the Euro.