Here is the bad news, low pressure will move from the central plains into the Great Lakes tonight and east of Montreal Wednesday. Warm air overrunning the cold air at the surface will produce a quick moderate snowfall for southern Quebec. The snow will mix with freezing rain and rain in southern Ontario. Expect snow to start in Montreal around 6pm Tuesday and taper off early Wednesday morning. A good 10cm (4 inches) is forecast for the Montreal area into eastern Ontario with perhaps a little more along the US border. Gusty southwest winds up to 60km/h may cause blowing snow early Wednesday. Skies will clear Wednesday, and it should be the mildest day in over 6 weeks with a forecast high above freezing. Weather warnings for freezing rain and snow stretch from the lower Great Lakes and Ontario into New England but not metro Montreal at this time.
The warmth will be short lived as colder weather is expected by Thursday morning with lows back down to -12C (10F) and highs of -7C (19F) for Montreal.