MONTREAL—A forecast for Montreal: the sound of sirens will ring out, warning drivers to remove cars from snowbanks or be towed; small tanks will relentlessly barrel down sidewalks clearing paths for pedestrians and giant snowblowers will transfer fallen snow from streets into long lines of transport trucks.

The snow-clearing effort is underway following Thursday’s massive storm and according to city officials it will likely only be complete after about seven days of hauling off the 45 centimeters of white stuff that descended onto the city in a short period Thursday.

Thursday's historic snowstorm wreaked wintry havoc on Montreal’s transportation system as all forms of travel were slowed to a crawl or cancelled outright.

The city had expected a storm but nothing like the swirling tempest that forced Environment Canada to drastically revise its forecast over the course of the day.

At least 45 centimetres had fallen on Montreal by day's end and 50 centimetres on its south-shore suburb, eclipsing the previous one-day recorded high of 43 centimetres set in March 1971, according to Environment Canada.

Montreal-area highways were plagued by slow-traffic, pile-ups and sporadic closures caused by slippery surfaces, heavy winds and blowing snow. By midday, the Montreal police appealed to motorists to stay off the roads if possible, in order to allow emergency vehicles easier passage in the difficult conditions.

Montreal city buses were delayed by hours and Laval’s bus service was cancelled completely throughout the day, only slowly restored during the evening rush hour. The Laval police resorted to installing chains on cars to race around the suburb.

Drivers also had difficulty climbing hills, where greasy roads led many to simply retreat downhill. A pileup involving 15 cars was reported on Highway 40 in the early afternoon about 50 kilometres west of Trois-Rivieres, but resulted in no serious injuries.

Still, police there were counting their blessings late Thursday.

The same storm had killed at least 16 people in the United States this week. Montreal's previous record blizzard in 1971 killed 17. But there was cause for optimism, as of Thursday evening, that Eastern Canada would be spared a similar human toll this time.

"There were no serious injuries," police Sgt. Martine Asselin said, speaking Thursday evening of the numerous Quebec road accidents. "We're lucky."

Because of the multi-car pileup, a stretch of the Trans-Canada Highway was shut down near Montreal, with provincial police using snowmobiles to access the closed portion of Highway 40.

There were other examples of authorities resorting to rare, even rustic, solutions.

For example, Hydro-Quebec used some old-fashioned travel techniques to reach customers who had lost power in a previous storm, days earlier.

"We're talking snowmobiles and snowshoes," said Hydro-Quebec spokeswoman Sophie Lamoureux.

She said 99 per cent of the customers who had lost power last week had their service restored, with the exceptions being customers in hard-to-reach outlying areas. Meanwhile, new outages were being reported with Thursday's storm.

Highway traffic rolled slowly throughout the day as accidents involving several trucks closed entire sections at a time.

During a press conference on Thursday afternoon, the City of Montreal announced that widespread snow clearing would start on Friday morning. Over 1,000 trucks were dispatches to the city’s streets to plow and spray abrasives.

Meteorologist René Héroux pointed out that the nature of the snow is different from that of last week, which was wet and heavy. He noted that this type of storm makes visibility and travel particularly difficult. 

Transport Quebec spokesman Bruno Lacombe also urged motorists to exercise caution due to blowing snow and slippery roads and sidewalks.

Another informed observer noted that it's the type of snowfall that's hard to love. "It's the combination of snow and blowing snow that makes this particularly nasty," said meteorologist Arnold Ashton.

Hundreds of flights were cancelled or delayed out of U.S. airports and, on Thursday, numerous departures were also cancelled at Canadian airports.

In Montreal, over a span of several hours Thursday afternoon, a majority of flights were either subjected to lengthy delays or cancelled entirely. A similar pattern was repeated in different Canadian cities as the storm spread east.

Travellers were urged to call ahead to check on their flight status before heading to the airports.

Southern Ontario was spared the worst of the storm.

Toronto received about 10 centimetres of snow into Thursday morning while the Niagara region and Hamilton area received 15 to 20 centimetres.

Still, Ontario Provincial Police said they were busy responding to numerous reports of vehicle accidents from Windsor all the way to the Greater Toronto Area.

They said most calls had been for minor fender-benders and one-vehicle collisions, except for one potentially serious incident in London on Wednesday.

West Region Sgt. Dave Rektor said an officer had his parked police cruiser rear-ended on Highway 401 around 5:30 p.m. when he went to assist another motorist who had driven into a ditch.

The officer was not injured because he was out of the car at the time, but the cruiser was extensively damaged.

In New Brunswick, blowing snow began falling midday Thursday in the southwest and eastern regions, with about 25 centimetres or more expected.

Parts of Nova Scotia and Prince Edward Island also lay in the storm's path, where winter storm watches or rainfall warnings had already been posted.

Environment Canada had said the Montreal region could receive up to 30 centimetres of snow accompanied by widespread blowing snow -- but that was before the storm hit the area harder than expected.

The tally was upgraded Thursday morning.

The city's previous record storm, in 1971, saw 47 centimetres of snowfall during a period of more than one day. That was aggravated by 110 km-per-hour winds, more than twice as powerful as what the city experienced Thursday.

Environment Canada recalls that the winds in that 1971 storm snapped power lines, causing people to go without electricity for up to 10 days.

—With files from The Canadian Press.