A winter storm that blanketed an already snowy Calgary made for a slippery morning commute Thursday and triggered the second snow route parking ban this week.

City officials say vehicles must be removed from designated snow routes by 10 a.m. Saturday to allow crews to clear those roads after as much as 20 centimetres came down since late Wednesday.

The treacherous driving conditions had police suggesting Calgarians stay home if possible. But, no such luck for most Calgary students — neither major school board called a snow day.

The Environment Canada winter storm warning for Calgary ended Thursday afternoon, after bringing down another 10 to 15 centimetres of snow on top of the 10 to 20 centimetres that had fallen by 6 a.m. Thursday.

The storm warning was still in effect for much of southern Alberta, with areas like Okotoks, Medicine Hat and Lethbridge expected to see another 25 to 35 centimetres before the snowfall tapers off in the evening.

However, Albertans will have something to look forward to. The agency's forecast calls for mostly sunny skies and warmer weather, with daily highs hovering around –5 C, beginning Friday and continuing through Wednesday.

The city says more than 70 pieces of snow-clearing equipment were out throughout the night trying to get the major routes ready for the morning commute Thursday. (Colleen Underwood/CBC)

Between 4 p.m. Wednesday and 4 a.m. Thursday there were 18 hit and run collisions, 69 non-injury collisions and eight involving injuries.

"We have just over 73 pieces of equipment on major routes throughout the city. We've done good overnight, but we did get a lot of snow," Calgary roads director Troy McLeod told the Calgary Eyeopener.

"It's winter driving conditions for sure."

Watch Calgarians navigate the fresh powder on their morning commutes 0:28

A snow route parking ban that went into effect Monday was lifted Wednesday at 7 a.m.

But officials declared another parking ban, to start Saturday at 10 a.m., said city spokesman Chris McGeachy.

Today, city crews are busy trying to clear Priority 1 roads, those that see 20,000 or more vehicles a day, such as Glenmore Trail and Crowchild Trail.

The parking ban is timed to come back into effect once the snow has stopped and crews are ready to clear Priority 2 routes, which include roads that get between 5,000 and 19,999 vehicles a day, such as Kensington Road and Acadia Drive. Many of these are on the city's snow routes. (You can see the snow routes marked on the city's map when a parking ban is imposed.)

The Blue Line LRT was running 45 minutes behind schedule because of a power issue until the problem was resolved by about 10:30, Calgary Transit said. Several buses are still running on detour routes because of the snow.

Schools open

Calgary public schools will be open as usual and yellow school buses service will be running, the Calgary Board of Education tweeted.

The Calgary Catholic School District website says its Calgary schools will also be open as usual. However, schools in Airdrie, Cochrane and Chestermere might close because they serve a large number of rural students.

The snowstorm has kept crews busy at the Calgary International Airport, where 41 pieces of snow removal equipment are working day and night to keep runways clear. (Calgary International Airport)

Parents are advised to check online and their emails for any changes.

Strathcona Tweedsmuir School in Okotoks is closed Thursday as well as Edelweiss Preparatory School in northwest Calgary.

Some highways closed

Conditions on highways around southern Alberta and into British Columbia were reported to be impassable in several spots.

Highway 1 was closed Thursday afternoon from the Alberta-B.C. border to Field due to high avalanche risk, and the road is not expected to re-open until Friday.

UPDATE - <a href="https://twitter.com/hashtag/BCHwy1?src=hash&ref_src=twsrc%5Etfw">#BCHwy1</a> Closed from <a href="https://twitter.com/hashtag/FieldBC?src=hash&ref_src=twsrc%5Etfw">#FieldBC</a> to the BC/Alberta border. Highway will remain closed until Fri Feb 9. Next update 9am PST. <a href="https://t.co/5fFCaadcR6">https://t.co/5fFCaadcR6</a> —@DriveBC

Highway 93 was also closed, between the Alberta-B.C. border and Radium Hot Springs, due to bad weather. That stretch also isn't expected to re-open until Saturday, Parks Canada said, due to avalanche risk.

Highway 519, between Highway 2 and Highway 811, near Granum, was closed due to a multi-vehicle collision on Thursday afternoon, as was westbound Highway 3 east of Lethbridge, also due to a collision.

RCMP said the southbound lanes of Highway 2 at Didsbury, about 75 kilometres north of Calgary, were impassable late Thursday morning after dangerous conditions let to multiple collisions and ditched vehicles. Southbound traffic on Highway 2 was being diverted at Township Road 582.

The Calgary International Airport is asking travelers to allow extra time to arrive for their flights and to check for cancellations or updated departure times.

Ten flights were listed as cancelled as of 11:30 a.m. on Thursday morning.

WestJet said it cancelled 16 flights on Wednesday in anticipation of the snowstorm.

"This thins out the schedule slightly to help ensure the de-icing process does not get backed up," said WestJet spokesperson Lauren Stewart in an email to CBC News. "So far, operations are normal and we are not experiencing any delays."