Calgary and large parts of Southern Alberta are under a snowfall warning, with up to 25 additional centimetres expected to fall by Tuesday.

In the areas around Cardston and Pincher Creek, up to one metre could come down with a winter storm warning in effect.

Calgary, which was exempt from earlier weather warnings, is already blanketed in snow and the roads are treacherous. Deerfoot Trail was snarled on Sunday morning as police dealt with multiple collisions. The city announced a snow route parking ban will start on Monday at 6 p.m.

That means vehicles won't be able to park on streets marked with a snow route sign for 72 hours.

A 72-hour snow route parking ban has been called for 6 p.m. Monday. (Mario De Ciccio/CBC)

"The parking bans are typically on our Priority 2 routes, which are mainly collector roadways and bus routes and we have to take care of our Priority 1 routes first," said city roads maintenance manager Bill Biensch.

"This is based on a forecasted snowfall of about 20 more centimetres. We need to take care of our major roadways first then move into our collector roadways. We're on the roads around the clock trying to improve conditions. Because it's continuing to snow we will continue to apply an abrasive to improve the traction on the road."

The last snow route parking ban was called in 2013.

Parking officials will ticket and possibly tow vehicles left parked on snow routes during the 72-hour ban.

According to numbers compiled by Calgary police, there were 158 crashes reported between 4 a.m. and 4 p.m. Sunday, with 10 of those involving injuries and 15 hit and runs.

Southern Alberta is blanketed in snowfall and winter storm warnings. (Environment Canada/screenshot)

"Be prepared to adjust your driving with changing road conditions. Surfaces such as highways, roads, walkways and parking lots may become difficult to navigate due to accumulating snow," said Environment Canada in its alert.

The areas of the province under a winter storm of snowfall warning include: