Heavy rainfall expected for southern Quebec

Most of snow is now gone in the Montreal region, but such is not the case in other parts of the province. Heavy rain on Thursday and Friday may lead to flooding in several regions, especially north and east of the city. A heavy rainfall warning has been posted by Environment Canada, with 20 to as much as 40mm expected.

Heavy Rainfall Warning posted for southern Quebec including metro Montreal.

Spring is well underway across southern Quebec, with mild temperature and rainfall expected. A slow moving, moisture-laden frontal boundary is forecast to move into the region on Thursday followed by low pressure moving northeast along the Atlantic coast. The combination of both systems will bring a prolonged period of wet weather to Montreal. After a sunny, mild Wednesday, clouds will increase, with rain developing Thursday morning. The rain may be heavy at times, with 20-30mm expected, and as much as 50mm along the US border. 

Showery weather will persist most of the day on Friday as well. Temperatures will be cooler than they have been, with daytime highs around 8C (48F) and lows near 3C (38F). The weekend will remain unsettled as an upper level low moves across the Great Lakes. Temperatures will be on the cool side, with more clouds than sun and a few isolated showers around.

The rain, combined with melting snow, will lead to areas of flooding, especially north and east of Montreal. I am not expecting any issues within the city, as most of the snow has melted. There may be some low lying areas that see ponding of water. There is however still plenty of ice on area rivers. For that reason Hydro Météo has watches in place for ice movement on rivers across far western Quebec, and in the Chaudière region.

April historically has produced some big snowstorms in Montreal. On April 9th, 2000, 34cm fell, with 32cm on April 1st, 1993, and just last year 5cm fell on April 21st. In 1975, a monster two-day storm produced 20 to 40cm of snow across large portions of the province, along with 90km/h winds. The winds created massive drifts and produced widespread damage especially in portions of the lower St. Lawrence. This will not be the case this year, there is no snow in our future.

The April 3-4, 1975 snowstorm hammered the province, with 30 to 40cm of snow, whipped by 90km/h winds. Montreal reported 26 hours with less than 1km visibility, while Québec City registered 11 consecutive hours of zero visibility. The barometric pressure dropped to 97.93 inches, equivalent to that of a Category 1 hurricane. Wind damage was widespread and roads were closed. (Photo Québecurbain)

At this time it looks like spring flooding will not be an issue in Montreal this year. Snowfall in the Montreal region was well-below normal in March and for the entire winter season. Only 23cm fell last month for a winter total of 180.2cm (70.9 inches) at Trudeau Airport. The long-term average is 209.5cm (82.5 inches). This is not the case in many other regions of Quebec, especially northeast of Montreal where the snowpack remains deep, and the risk for spring flooding is much higher. For example parts of the Gaspé and Saquenay regions had over 100cm of snow in March alone. There is still 127cm of snow on the ground in Sept-Îles compared to the normal of 40cm.