Large parts of Ontario and Quebec are expected to experience heavy rainfall this week as remnants of tropical storm Debby make their way from the United States into Canada, scientists at Environment and Climate Change Canada said on Thursday.
The storm, which is currently over the Carolinas, is expected to move towards Canada.
“It is forecast to accelerate and weaken into a tropical depression as it tracks across the eastern United States today, ultimately becoming post-tropical on Friday,” Jennifer Smith, national warning preparedness meteorologist at Environment Canada, told reporters.
Smith said the remnants of the storm will interact with a low-pressure system over the Great Lakes. This could bring impactful rainfall before the storm moves east into Atlantic Canada.
“An added challenge to the forecast is the likelihood of showers and thunderstorms to develop across eastern Ontario and southern Quebec, ahead of the arrival of the remnants of Debby, enhancing rain totals in those regions,” Smith said.
She said rainfall could begin as early as Thursday. Showers, possibly thunderstorms, are expected to develop across eastern Ontario, including southwestern Ontario from Toronto to Georgian Bay, and Algonquin Park east to southern Quebec, including Montreal and the Laurentians.
From Friday into Saturday, the storm is likely to move over eastern Quebec and northwest New Brunswick, bringing significant rainfall to the Saint Lawrence River Valley and Quebec City.
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The weather system will begin to weaken by Sunday, as it moves to Newfoundland and Labrador, before moving out to the Labrador Sea, Smith said, adding that some regions could see flash flooding along with significant rainfall.
“Many regions, particularly a wide corridor from Cornwall to Quebec City, will see rainfall amounts exceeding 50 millimetres and localized rainfall totals over 100 mm,” she said. “Significant impacts may occur in large urban centres such as Ottawa and Montreal, and possibly even Toronto, especially if a heavy shower develops over a prone area.”
Smith said the bulk of the rainfall over Ottawa and Montreal is likely to occur between Friday morning and late Friday night, before the system moves east on Saturday.
“It is important to be vigilant and to follow online for warnings and forecasts issued by Environment and Climate Change Canada as weekend plans are being made,” she said.