Motorists were advised to stay off the roads in the GTA through Friday night as snow levels reached as much as 36 centimetres in some areas.

Police cited poor road conditions in a fatal three-vehicle collision in Pickering earlier in the day that killed a 49-year-old Oshawa man. Numerous other collisions were reported on GTA roads throughout the day.

By the afternoon, the Ontario Provincial Police had received more than 600 calls for service since midnight, according to Sgt. Dave Woodford. More than 350 of them were for collisions in the GTA.

“Drivers have to realise they’re responsible for their actions; they need to keep the speeds down in order to keep everybody on the roads safe,” Const. Clint Stibbe told CTV Toronto.

Throughout the day, the transport ministry deployed more than 350 salters and plows, as well as 1,300 snow plow operators.

Still, drivers were frustrated.

“They were nowhere near prepared for this,” one motorist said.

But according to the MTO, snow plows were simply overwhelmed by the number of motorists on the road and needed a chance to catch up.

Director of Transportation Peter Noehammer said the biggest challenge to snow clearing was the traffic and cars on the streets.

"People could tuck their cars into their driveway, that would really help us out as we plow the streets later on today," he said.

A snowfall warning remained in effect for almost all of southern Ontario, with Environment Canada predicting 20-30 centimetres of snow for Toronto by day’s end. The snow is expected to taper off over South Central Ontario this evening and Eastern Ontario near midnight as the system heads east, the agency said.

Geoff Coulson, a warning preparedness meteorologist with Environment Canada, told CTV News Channel that as much as 40 cm of snow could end up on the ground in localized areas by the end of the night.

Environment Canada senior climatologist David Phillips said Toronto hasn’t seen snowfall over 15 centimetres since Dec. 19, 2008.

“In the scheme of things it’s not a record, but in terms of what we’ve seen in the relatively near past, it is a big one,” Phillips told The Canadian Press.

Several private schools and public school boards across southern Ontario were closed Friday due to weather conditions.

The weather also forced several universities and colleges, including York and Ryerson, to cancel classes, and in some cases, postponed scheduled exams.

After cancelling almost 40 per cent of flights Friday, Toronto Pearson International Airport is encouraging travellers to check flight information before trekking out to the airport.

With a report from Janice Golding and with files from The Canadian Press