Snowplows clear snow on Highway 401 at Avenue Road in Toronto early Thursday due to the first heavy snowfall of the season in Ontario and Quebec.Snowplows clear snow on Highway 401 at Avenue Road in Toronto early Thursday due to the first heavy snowfall of the season in Ontario and Quebec. ((Tony Smyth/CBC))

A major winter storm that had its beginnings in the U.S. South and has been linked to several deaths blew into Eastern Canada overnight, prompting storm warnings and flight cancellations.

Environment Canada had winter storm warnings posted for portions of eastern Ontario and southern Quebec along the St. Lawrence River. Warnings that had been in place for areas stretching from Picton to Kingston and Brockville were lifted shortly after 9:30 a.m. ET.

The storm was expected to dump 15 to 20 centimetres of snow in areas of eastern Ontario along the St. Lawrence River.

The areas of Smiths Falls, Ottawa, Prescott and Russell, and Gatineau were all under a snowfall warning, with Environment Canada predicting 15 cm Thursday.

CBC meteorologist Jay Scotland said the highest snowfall totals are expected south and east of the St. Lawrence, with Environment Canada saying there could be up to 45 centimetres in portions of southern Quebec.

Warnings also covered all of New Brunswick and western Prince Edward Island. Parts of Nova Scotia are under a winter storm watch, and there's a rainfall warning for southern portions of the province.

The storm is expected to move to Newfoundland and Labrador with strong winds beginning Thursday night and peaking on Friday. Snowfall totals for the inland portions of the south and west coasts are expected to top 10 centimetres by Saturday morning, with 15 centimetres of accumulation by the end of Saturday for central and northeastern Newfoundland.

Travel troubles

Roads throughout the Toronto region, where about 10 centimetres were on the ground, as well as the Montreal area were mostly snow covered.

Ontario Provincial Police reported dozens of accidents on highways in the Greater Toronto Area.

CBC Montreal weather specialist Sabrina Maradola reported reduced visibility and slick conditions on the city's streets with cars getting stuck in the snow or veering off roads.

"If you don't have to go out, if you are on holiday, take advantage and do stay home today," she said. "It's not the best day to be on the roads."

At Canada's busiest airport, Pearson in suburban Toronto, 28 arriving flights and 46 departures were cancelled by 8:39 a.m. Thursday, while many more flights were delayed. There were also cancellations reported at Trudeau airport in Montreal.

The storm system originated in the U.S. earlier this week, in parts of the southern and central U.S, where it has been blamed on the deaths of at least 12 people.

Thousands of homes are without power as states report record amounts of snowfall.

National Weather Service spokesman David Roth said the U.S. Northeast's heaviest snowfall would be in northern Pennsylvania, upstate New York and inland sections of several New England states before the storm ends Friday morning.

More than 30 tornadoes were reported, arriving with little warning on Christmas Day in the Gulf Coast region.

For more information on local storm conditions, please check your CBC local website:

With files from The Associated Press