Before I get to the long range, a strong high pressure ridge over the U.S. midsection will start to send heat and humidity up through the northern U.S. Plains and Canadian Prairies through the weekend then eastward into the Midwest later in the weekend and early next week.
The hot and humid air will encounter resistance across the Great Lakes and Ontario Sunday and Monday and the result will be a cluster of potentially strong thunderstorms running east then southeast around the northeast periphery of the high pressure ridge.
Right now, I see the potential for severe thunderstorms over southern Manitoba Friday night into Saturday. Strong thunderstorms could impact southern Ontario and perhaps southern Quebec by Monday. More on that later.
This is my latest interpretation of the ECMWF model long-range output through Sept. 16-22.
The ECMWF is clearly indicating that there will be a significant increase in Atlantic Basin tropical activity during September, which is also normally the peak month for hurricanes and tropical storms.
It does look like the model is indicating that the greatest threat for tropical storms or hurricanes will be in the Caribbean and then into the Gulf of Mexico.
The model also predicts that the Southwest U.S. monsoon will be picking up as tropical air is drawn northward into the region.
Wildfire smoke causing significant problems across Saskatchewan.
Spring-like storm to soak parts of eastern and Atlantic Canada this weekend as the West cooks.
Heat wave for western Canada by the weekend as the East cools down a bit.
Severe weather threat Monday evening/night for Ontario. Building heat wave late this week into next week out West.
My latest interpretation of the weekly ECMWF forecast model output.
Potential for heavy rain and strong thunderstorms for parts of eastern Canada Friday while cooler air spreads into the West.