Forest fire smoke diminishes severe weather in Montreal

Dense smoke from northern Ontario wildfires turns day into night in Thunder Bay on Tuesday afternoon. Thunder Bay was one of the warmest locations in the country on Monday, surpassing 40C (104F). Fires have exploded across that region, sending smoke drifting across southern Ontario and into southwestern Quebec. The smoke has resulted in hazy sunshine and very poor air quality. (Sarah Law/CBC)

Plumes of smoke are drifting across Ontario and southern Quebec on Wednesday from massive forest and wildfires burning across northwest Ontario. At least a dozen new fires have erupted this week, fueled by intense heat, over 40C in some locations, and widespread lighting strikes. To date over 450 fires have been reported in Ontario, with 302 in Quebec. Several are burning out of control in both provinces, resulting in very poor air quality across eastern Canada and the United States.

In fact, early Wednesday morning, Toronto had the poorest air quality of any major city in the world, with a AQI rating of 192, in the unhealthy range. Montreal sits at 73 by comparison, in the moderate range. Air quality advisories are widespread across Ontario. The smoke is obscuring the sun and resulting in a very smokey smell in the air. 

Gusty west winds up to 50km/h are helping to spread the smoke across southwestern Quebec. Conditions will remain poor into Thursday before the arrival of a cold front pushes the smoke south.

The smoke on Tuesday managed to cap the atmosphere here in southern Quebec, resulting in a greatly diminished thunderstorm threat. Capping the atmosphere occurs when warmer air aloft and cooler air at the surface, results in supressing vertical air movement and thus thunderstorm development. Temperatures across our region were around 30C (86F) as opposed to the middle 30s (90s) that were forecast.

Despite the cap, storms still developed, some severe, but the threat was greatly reduced during the daylight hours. Stronger storms did occur after dark, but mainly west of Montreal and south into New York. Those storms produced large hail in parts of the Ottawa Valley as well as the Seaway Valley of upstate New York into the Adirondacks.

The storms did result in over 10,000 lightning strikes over a 24 hour period from Ontario across southern Quebec and into the northeastern US. Earlier in the day Tuesday, a swath of strong storms affected the region between Montréal and Quebec City, southeast across the Eastern Townships prompting a tornado watch by Environment Canada. As I write, no tornadoes were reported.

The weather will remain hazy and warm in Montreal through Thursday.