Tropical storm Debby brings flash flooding risk to Ontario, Quebec; rainy, windy weekend for Atlantic Canada

The centre of tropical storm Debby was located 200 kilometres southeast of Charlotte, North Carolina near noon on Thursday.

The storm impacted parts of Florida and the Carolinas since this past weekend with power outages, tornadoes, and flooding.

Debby speeds northward on Friday, combining with a separate weather front moving across the Great Lakes. While the storm loses its tropical structure as it moves north, it still contains a tremendous amount of moisture. A swath of heavy rain is expected to track along with the storm through parts of the eastern U.S., into eastern Ontario, and then the St. Lawrence River Valley in Quebec.

The path of Debby as it becomes post-tropical and speeds northward over the next few days. (Source: CTV News Atlantic)

Heavy rain, risk of flooding in Ontario, Quebec

Rainfall warnings have been issued in Ontario from Peterborough north to Petawawa and then east to Ottawa. Rain amounts of 50-to-75 mm or more expected Thursday night through Friday. Environment Canada cautions “heavy downpours can cause flash floods and water pooling on roads. Localized flooding in low-lying areas is possible.”

Toronto is under a Special Weather Statement with rain amounts of 25-to-50 mm expected with the rain heavy at times Thursday evening into Friday.

Rainfall warnings are also in place across a large area of southern Quebec, including Montreal, Quebec City, and the Eastern Townships. Rain amounts of 50-to-100 mm are possible Friday into Friday night. Those areas are also advised localized flooding in low-lying areas is possible.

A swath of heavy rain is expected to track through parts of the eastern U.S. and into eastern Ontario/southern Quebec as the remnants of Debby move north. (Source: CTV News Atlantic)

Rain, wind in the Maritimes

Scattered showers will develop in western parts of the Maritimes during the day on Friday. Rain and showers will become more widespread Friday night and continue into Saturday. By Saturday afternoon and evening the remaining rain is mostly expected to be in the form of scattered showers.

For most of the Maritimes, rain totals are expected to range from 10-to-30 mm, which shouldn’t cause much in the way of water issues. Western areas of New Brunswick should continue to monitor the forecast as some guidance has indicated pockets of 30-to-50 mm of rain may be possible there.

A windy Saturday is expected for the Maritimes. A southwesterly wind will increase to peak with gusts of 50-to-70 km/h Saturday morning and afternoon. The wind will diminish Saturday evening into Sunday morning. You may wish to secure any light, easily windblown objects on Friday.

A gusty southwest wind develops across the Maritimes on Saturday. The wind easing Saturday night into Sunday. (Source: CTV News Atlantic)

Newfoundland and Labrador

The remnants of Debby will cross the Gulf of St. Lawrence and move across northern Newfoundland Saturday afternoon and evening. Rain and showers are expected across Newfoundland and southern Labrador Saturday and Saturday night.

Rainfall amounts are forecast in a general range of 10-to-30 mm. There is a risk of higher rain amounts in the mountainous terrain of western Newfoundland. Pockets of 50-to-75 mm or more of rain are indicated as being possible north of Corner Brook and towards Port Saunders on the Northern Peninsula.

A southwesterly wind will increase for Newfoundland Saturday afternoon into Saturday night. Peak gusts will reach 40-to-60 km/h. Gusts on exposed areas of the southern coastline as highs as 60-to-75 km/h. The wind is forecast to diminish through Sunday.