Ontario's duelling weather threat: Snow in the north, flood threats in the south

Significant snowfall and flood concerns are underway in Ontario as a potent Colorado low will bring a true tale of two seasons this week, with both significant snow and flooding rains targeting different parts of Ontario through Wednesday. There's even the chance for rumbles of thunder with some heightened instability across the south.

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Because of the amount of rainfall and warming temperatures expected in southern Ontario, there is a raised threat of localized flooding and ice jams as the low pushes through. Local conservation authorities are on alert for possible river flooding.

Meanwhile, winter storm warnings cover sections of northern Ontario, with heavy snow and reduced visibility expected to impact travel. Drivers are urged to postpone non-essential travel until conditions improve. Impacts from the storm span over 2000 km from Central Canada into the Maritimes.

Stay up-to-date on your local weather alerts, and be sure to check the latest highway conditions before heading out on the roads.

Tale of two seasons with messy impacts in between

Ontario began to climb out of the freezer on Monday, with the warm-up arriving courtesy of a system approaching from the U.S. Mild and rainy systems have been few and far between in Ontario so far this winter.

Wednesday will be the main event for northern and southern Ontario as heavy rain and snow fill in across the province. Widespread warnings are in effect.

Southern Ontario: Flood and ice jam threats grow

While southern Ontario will find itself on the milder end of the low, the region could still see a brief dose of icy precipitation as the warm front arrives on Tuesday.

By the afternoon, with the warmer temperatures, expect a changeover to rain in the southern sections. Meanwhile, a burst of snow is expected in Ottawa, where about 5 cm is forecast to fall.

Expect Wednesday to be a washout across the southern and eastern sections of the province.

A swath of 10-30 mm of rainfall is possible, elevating the localized flood risk with rapid snowmelt, particularly in areas with a considerable snowpack. Ice jams will also be possible, so ensure your gutters are clear of any snow and ice.

March thunderstorms Wednesday? More snowfall Thursday?

Southern Ontario, including the Greater Toronto Area (GTA), could even hear a rumble or two with a little more instability and dynamics in place on Wednesday. Expect steady rainfall Wednesday morning with breaks through the afternoon with isolated heavy showers,

The most favourable setup for severe weather, however, will remain far south of the border.

As the storm exits east out of the province on Thursday, a noticeable drop in temperatures will see rainfall change into blowing snow for parts of southern and eastern Ontario.

Expect 40-50 km/h wind gusts and bouts of snowfall which could slow travel Thursday morning. The Greater Ottawa Area may also see snowfall during the Thursday evening commute.

Colder-than-normal temperatures are expected through the weekend, but will then trend much milder during the following week. Above-seasonal temperatures are expected to dominate from mid-March into near the end of the month.

Northern Ontario: Winter storm warnings for significant snowfall

Meanwhile, more wintry weather will be felt in parts of northern Ontario as it will be on the colder side of the low.

The system will dump heavy snowfall and generate blustery winds on Wednesday, leading to treacherous winter weather near Sudbury, North Bay, Sault Ste. Marie and Timmins.

A swath of 10-20+ cm of snow is possible, with hazardous travel expected on Highway 11 and Highway 17. In Timmins, between 20-30 cm of snow could fall.

Blowing snow is then expected on Thursday as the storm exits east, especially for some of the snowbelt regions.

Stay with The Weather Network for all the latest on conditions across Ontario.

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