Soaking rain for Montreal and eastern Canada

A frontal boundary will deliver 25 to 50mm of rain to southern Ontario and Quebec on Thursday. Meanwhile tropical storm Elsa will bring heavy rain and wind to the eastern portion of the province.

A low pressure trough pushing eastward across Ontario and Quebec will deliver heavy rain and thunderstorms to both provinces on Thursday. The bulk of the rain in Montreal will fall this afternoon into the overnight hours. A few of the thunderstorms may be strong, with heavy downpours the main threat. Most areas are expecting 25-35mm of rain, but over 50mm is possible locally across the St. Lawrence Valley in Ontario. We remain in a rather sharp deficit as far as rainfall goes, so the threat for flooding is minimal. However there could still be some ponding of water on roadways. 

Temperatures will be cool today across southern Quebec, in the 15 to 20C range (60-70F). Warmer weather returns for the weekend along with a spike in humidity levels starting Sunday and persisting into next week.

Further east across the lower St. Lawrence and into New Brunswick, the aforementioned trough will tap into tropical moisture moving along the Atlantic coast from Elsa. Portions of central New Brunswick could see up to 100mm (4 inches) of rainfall. 

Early Thursday morning, Elsa was located 240km southwest of Raleigh, North Carolina. Elsa was still a tropical storm, moving northeast at 30km/h, with winds of 65km/h. Tropical storm force winds are expanding over a wide area, reaching out 185km from the center of the storm.

Tropical storm Elsa is forecast to move from the Carolinas into Atlantic Canada over the next 24 hours. (Canadian Hurricane Centre)

Elsa has been delivering heavy rain along her path along with isolated tornadoes. The center of the storm will move across the middle Atlantic states on Thursday and into southern coastal New England tonight. There may be s light increase in intensity once the center moves back over open water Thursday afternoon. On Friday, Elsa will approach DownEast Maine, Nova Scotia, New Brunswick and Prince Edward Island as a potent post-tropical cyclone. Heavy rain has prompted widespread flood watches across southern New England. Watches and warnings will likely be extended into New Brunswick and Nova Scotia later today. Along with the heavy rain, gusty winds up to 70km/h are possible.