Strong low pressure to impact southern Ontario & Quebec

Strengthening low pressure will move from the middle Atlantic region into southern Quebec by tonight. Very mild air will result in rain for much of southern Quebec. Much colder air returns late tonight and Sunday, with perhaps a few centimetres of snow. (AccuWeather.com)

Widespread rainfall and freezing rain warnings are in effect early Saturday morning as deepening low pressure lifts north from Maryland towards the Champlain Valley later today. The storm is carrying abundant moisture with it, with up to 25mm of rain forecast across the region. Temperatures are hovering near the freezing point this morning, with 0.9C here on Ile Perrot, with 5mm of rain falling so far. They will warm today as gusty southeast winds develop, up to 5C (41F).

The storm will continue to strengthen as it approaches the Vermont/Quebec border late tonight and moves into eastern Quebec Sunday. As it does so, much colder air will begin to wrap around the backside of the system and into Ontario and southwestern Quebec. Rain should begin to change to snow late this afternoon in Ontario and tonight in Montreal. Snowfall amounts will range from 2 to 3cm in Montreal, to as much as 10cm in parts of the St. Lawrence Valley of Ontario and New York. Roads will become slick as temperatures head below freezing and down to -7C by Sunday afternoon.

In addition to the colder temperatures, winds will increase out of the west and northwest, up to 70km/h into Sunday.

Further north and west across portions of central Quebec, heavy snow and freezing rain are forecast with as much as 30cm expected. Travel conditions are extremely poor today in those regions.

Precipitation will taper off to flurries early Sunday, along with blustery and colder conditions. The colder air is with us now through Christmas Day, with a few chances for light snow, but no major storms on the horizon for Montreal at this time.