Wednesday, August 02, 2017

More strong thunderstorms possible through Friday

Flooding after Monday's severe thunderstorm under Cote-de-Liesse at Hickmore. Firefighters opened the manhole cover to release the flood waters. (CTV News)
Warm and humid weather is expected to continue Wednesday through Friday across metro Montreal. Montreal has not recorded a 30C plus temperature since June 18, when the mercury hit 32.1C (90F). The 30C free month of July, was only the eighth time in recorded history that this has occurred in Montreal. Weather records at Trudeau date back to 1942. The streak will come to an end today, if the city reaches the forecast high of 31C (88F). Strong thunderstorms are possible this afternoon, and again right through Friday evening, as the warm and humid air remains in place. Several impulses of energy will rotate through the warm air mass, generating the thunderstorms. Any storms that do develop will be possible of producing heavy rain, just like the storm Monday afternoon in central Montreal.

Flood waters gather in the parking lot along the Trans Canada Highway at Cote-Vertu on Monday, July 31. (Valley Weather)

Severe Thunderstorm Produces Flooding
On Monday afternoon, a strong isolated thunderstorm cell moved from Laval across north central Montreal towards Trudeau Airport between 4 and 5pm. The storm brought torrential rain, with between 33mm and 37mm falling in less than one hour in Saint Laurent and Dorval. The result was flooding of several basements and highways. Our parking garage and ramp here at The Suburban flooded rapidly from the torrential rain. Strong wind gusts in excess of 85km/h brought down several trees. Lightning and wind knocked out power to over 17,000 Hydro Quebec customers in metro Montreal. The thunderstorm also produced pea size hail. The storm rapidly dissipated as it swept southeast across the Island of Montreal. The isolated nature of this particular storm produced the heavy rain and flooding in a narrow swath through the city. I measured no rain at all on L'Ile Perrot, just 20 kilomteres to the southwest of Trudeau Airport.

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