Friday, July 09, 2010

Flooding possible today

Dog Days of Summer

This photo was sent to me yesterday, I am not sure of the source,
but boy does he have the right idea!

12:30pm Update: Warnings for heavy rain have been extended across all of eastern Ontario including the National Capital District. Heavy, slow moving thunderstorms are also developing ahead of the cold front in the tropical air over our region. Radar is showing several storms southwest of Montreal moving towards the city. The bulk of the heavy steady rain is still west of Ottawa. It is hot again in Montreal, 30C at noon with a humidex of 40C.

8:36 Update:
Radar is showing thunderstorms with heavy rain stretching from the Ottawa Valley to Lake Ontario moving very slowly east towards east central Ontario. The first indications that these storms will be soakers is in the form of Heavy Rain Warnings now posted from Renfrew to Peterborough in Ontario for 40-60mm of rain or more. I imagine these will be the first of many warnings today.

As the heatwave moves into day 5, relief is on the way in the form of a very slow moving cold front. The front has been crawling across Ontario towards western Quebec and the St. Lawrence Valley. Concern is increasing for flooding, and at this unusual hour of the morning and well in advance of the front arriving in southern Quebec, Environment Canada has posted a severe thunderstorm watch for metro Montreal and the surrounding region. The storms today will be slow moving in nature and dripping wet with moisture. The potential exists for 50mm or more of rain in a very short period of time. The concern is so great that flash flood watches have been posted for all of New York State and Vermont. The storms will develop in the tropical air by noon and persist into this evening. The threat for wind damage or hail is not that great, the main threat will be flooding. Historically heatwaves don't just fade away they end with an event. Keep in mind the Decarie flood of July 14, 1987.

Speaking of heat Thursday was another impressive day. Many locations including Ottawa, Kemptville, St Anicet, Gatineau and up into the lower Laurentians reached or exceeded 35C. At 3pm yesterday afternoon St. Anicet on the shores of the St. Lawrence River was 35C with a humidex of 46C. Burlington, Vermont won the heat award yesterday, reaching 36C and tying a long standing record. Montreal reached 34C beating the record of 33C from 2008.

I will post more information today on the flood potential as the threat develops.

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