Just under 24 hours after issuing a special weather statement for Toronto ahead of this weekend's expected megastorm, Environment Canada has issued yet another special alert — this one an official snowfall warning.

"Persons in or near this area should be on the lookout for adverse weather conditions and take necessary safety precautions," wrote the federal weather agency in its alert, issued at 3:21 p.m. on Friday.

"Snow is expected to move into the area on Saturday morning as a low pressure system approaches. Snow will be heavy at times Saturday morning and afternoon," the warning continues. 

"Winds gusting up to 60 km/h will create areas of blowing snow giving reduced visibilities, particularly Saturday afternoon and Saturday evening."

First snowfall warning of 2020 issued for much of Southern Ontario! Expect 10-15cm for GTA, closer to 20cm in Eastern Ontario and Ottawa Region.#ONstorm https://t.co/JyRsBkRoOc

— Nic Tam (@nictamhk) January 17, 2020

Four minutes after issuing the snowfall warning, Environment Canada cancelled the less-severe alert it had sent out for Toronto on Thursday afternoon.

That now-cancelled special weather statement warned that Toronto could see up to 15 cm of snow between Friday and Saturday thanks to a low pressure system moving across the Golden Horseshoe, with winds of up to 60 km/h creating treacherous travel conditions.

The forecast does not appear to have changed, though Environment Canada's upgrade of the notice — from an advisory to an official warning — suggests that we may be in for more hazardous weather than initially predicted.

"Prepare for quickly changing and deteriorating travel conditions," reads the snowfall waarning. "Visibility may be suddenly reduced at times in heavy snow."