Winter storm approaching southern Ontario

March 01, 2018

From record-breaking warmth to the most lion-like roar into March, an incoming blast of heavy snow will as a powerful reminder that winter is still fully in charge. Prepare for blowing snow and very poor visibility starting tonight.

"One of the most significant winter storms of the season is set to hit southern Ontario with widespread impacts and travel delays likely," says Weather Network meteorologist Tyler Hamilton. "This system features deep amounts of Atlantic moisture wrapping into the low, therefore snowfall amounts will be significant for the hardest hit areas."

Travel on Thursday, not advised

This complex weather system will pass south of southern Ontario late Thursday with wrap around snow expected to continue on Friday.

"Rain or mixed precipitation has already changed over to accumulating snow in the Windsor area, and the same changeover will occur in the Chatham area by early this evening," Environment Canada said in a snowfall warning late Thursday afternoon. "Snow, heavy at times, will then continue through this evening. Total snowfall amounts of 15 to possibly 20 centimetres are likely by early Friday morning."

Winter storm warnings also spread east to the Hamilton, Niagara and the Halton-Peel region, with the heaviest snow expected overnight. Quickly deteriorating conditions are expected especially along the QEW from Hamilton to St. Catherines.
"Consequently, paired with gusty northerly winds, there is significant confidence there will be issues with blowing snow and travel issues lingering through Friday morning," Hamilton says.

Sufficient cooling throughout the atmosphere combined with a southern track of the low gives high confidence that the precipitation turns to all snow throughout the evening hours Thursday and pre-dawn on Friday.

"Wind gusts are building to 60 km/h across the Greater Toronto Area by Thursday evening, while regions of the northern Niagara Peninsula will see winds gusting to over 70 km/h with extensive blowing snow before easing Friday morning," Hamilton says. "Visibility will be greatly reduced during these time periods."

Major commute issues likely Friday morning

For areas near Lake Ontario and the Niagara Peninsula, expect a difficult Friday morning commute with lingering blowing snow.

"By late morning into the early afternoon on Friday, snow intensity decreases," Hamilton says. "But look for some lingering snowfall accumulations near Niagara."

Snowfall Totals

The system will bring a large range in snowfall accumulations. The heaviest amounts of 15-30 cm will fall in Niagara, near the north shore of Lake Erie and across the eastern half of the region.

"Snow totals will steadily decrease from south to north across the GTA," adds Dr. Doug Gillham, another meteorologist at The Weather Network. "The southern GTA and Hamilton area should see 10 to 15 cm, with 5 to 10 cm expected for downtown Toronto."

Less than 5 cm is expected across northern parts of the region, including Newmarket to Barrie and east to Peterborough.

"These totals will be updated mid-morning," says Gillham. "There are models that have a much sharper northern edge to this system. If that occurs, then we will lower totals for downtown Toronto and for the northern GTA."

This is a difficult forecast, here's why

Two potent pieces of energy are barreling towards the Great Lakes, forming a large and slow-moving system near Lake Erie. The key here is that the storm will be strengthening over the region with impressive atmospheric dynamics and a stream of Atlantic moisture feeding in from the east, leading to widespread precipitation. But with temperatures hovering near the freezing mark this quickly becomes a difficult forecast.

This type of strengthening storm combined with its track near Lake Erie, puts areas of southern Ontario in line to receive a heavy, but narrow band of snow.

"It's also kind of interesting that we're talking about a winter storm, but it will take on a spring-like characteristic: strong convection," says Weather Network meteorologist Erin Wenckstern. "With a convective type of storm, it basically means that precipitation rates will be on the increase and in this case, a lot of that precipitation will fall as snow." 

Heavier rates will also force a faster transition from rain to snow in many areas, also adding to its complicated nature. 

"This is what makes forecasting snowfall amounts particularly difficult to nail down since accumulations will vary significantly and some areas can become snowfall overachievers," Wenckstern adds.

Smooth sailing into spring after this?

March is still a winter month and has the reputation for bringing periods of volatile weather, however, signs are pointing to an end to the severe and persistent cold weather for the month. Just don't let your guard down completely.

"Winter will still have some parting shots and it is not clear sailing straight through spring," Gillham warns. "Early and mid-March will bring periods of more typical March weather with the potential for snow at times, but "seasonal" steadily climbs through the month and there are increasing signs of another period of well above seasonal temperatures later in the month."

Taken from The Weather Network

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