Winter storm warning posted for southern Quebec

Light freezing rain is already falling Sunday afternoon across many parts of southern Quebec and Ontario. The precipitation should transition back to heavy wet snow this evening and overnight, with 10-15cm possible in Montreal, Ottawa, and Quebec City.

Winter Storm Warning for southwestern Quebec, eastern Ontario, the Adirondacks and Green Mountains. Winter weather advisory for northern New York and portions of Vermont.

Expect slick and dangerous travel conditions today through Monday morning.

A messy mix of precipitation is expected across southern Quebec and eastern Ontario over the next 24 hours. Low pressure over the Great Lakes will move just south of Montreal tonight, while a second area of low pressure develops along the New England coast and move northeast towards Atlantic Canada.

Precipitation has already overspread the region Sunday afternoon, with freezing rain and rain from Montreal southward, and wet snow north and east of the city. As marginally colder air filters into the St. Lawrence Valley late Sunday afternoon, all precipitation should change back to wet snow and become heavy at times overnight. A general 10 to 15cm is forecast for Montreal and Ottawa, with more north of the city and less south towards the US border.

Gusty northeast winds of 30-50km/h will accompany the snow, putting stress on tree limbs and power lines. Temperatures will remain nearly stationary throughout the period, around 0C (32F) for Montreal. As the precipitation tapers off to flurries Monday afternoon, temperature will drop, to lows of around -5C (23F) by Tuesday morning.

Expect icy and snow covered roads at times over the next 24 hours. I imagine the Monday morning commute will be very challenging, especially for those off island to the west, where the Iles aux Tourtes bridge is down to only one lane in each direction for the foreseeable future. Give yourself plenty of extra time.