Canada: Adverse weather forecast across eastern Ontario and western Quebec through at least early Nov. 1

Severe weather is forecast across parts of eastern Ontario and western Quebec through at least early Nov. 1. Severe thunderstorms are ongoing across parts of eastern Ontario on Oct. 30 and are expected to track into western Quebec throughout the day. Strong wind gusts, hail, and lightning may accompany storms. Heavy rainfall is expected in areas further south in eastern Ontario from Oct. 30 through the morning of Nov. 1. Across a wider area of eastern Ontario, rain is expected Oct. 30-31 before transitioning into the first accumulating snowfall of the season during the afternoon Oct. 31, with freezing rain possible in places. Flooding is possible in areas where heavy rainfall occurs, and hazardous travel conditions are likely in areas where more wintry precipitation falls due to slippery roads and reduced visibility caused by blowing snow.

As of Oct. 30, Environment Canada has issued red severe thunderstorm warnings (the highest level on a three-tier scale) for parts of Little Abitibi-Kesagami Lake and Timmins-Cochrane-Iroquois Falls forecast districts in Ontario. Severe thunderstorm watches are in place across the affected areas in western Quebec. Red heavy rainfall warnings have been issued for parts of Blind River-Thessalon, Elliot Lake-Ranger Lake, and Salut Ste. Marie-St. Joseph Island and Searchmont-Montreal River Harbour-Batchawana Bay forecast districts in Ontario. Grey special weather statements for accumulating snowfall and freezing rain are in place across parts of eastern Ontario. Officials may update and extend the coverage of weather alerts over the coming hours.

The storm system could produce rounds of heavy precipitation (including rain and snow) and strong winds across the affected area. Where precipitation falls as rain, flash and areal flooding is possible. Such flooding is possible in low-lying communities near watercourses and other large bodies of water, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites located downstream of large reservoirs may be subject to flash flooding after relatively short periods of intense rainfall. Precipitation could fall as snow in parts of the affected area over the coming days. Wind gusts could cause blowing and drifting snow; decreased visibility is likely in these areas.

Floodwaters and related debris may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around the affected area. Flooding in urban areas could also result in significant traffic congestion. Heavy snow will likely make driving hazardous in some areas; authorities could implement temporary road closures or detours in such locations.

The disruptive weather will likely cause some delays and cancellations at airports in the region. Flooding or snow could block regional rail lines; freight and passenger train delays and cancellations are possible in areas that see heavy rainfall or snowfall due to potential track blockages.

Disruptions triggered by inclement weather and resultant hazards, such as flooding or snowfall accumulations, could persist well after conditions have improved—it could take days before floodwaters recede and/or officials clear debris. If there is severe damage to infrastructure, repair or reconstruction efforts may result in residual disruptions.