The combination of a slow-moving storm system, higher dew points and instability will lead to a three-day period of severe thunderstorms from the central Prairies to northwestern Ontario.
The main threats will be damaging winds and large hail. The tornado threat looks low at this point.
For Thursday, the main area for severe thunderstorms looks to be the southeastern quarter of Saskatchewan later in the afternoon and evening.
For Friday, The threat continues for southeastern Saskatchewan but also spreads into southwestern Manitoba.
By Saturday, strong to severe thunderstorms are possible from south-central Manitoba into northwestern Ontario.
Behind this system, cooler air will spread into the Prairies over the weekend and into early next week.
Very warm and humid conditions for eastern and parts of Atlantic Canada early next week as a south to southwest flow of air takes hold. This should be a fairly short period of uncomfortable conditions before another front arrives.
During this period, I expect temperatures to average anywhere from 3 to 7 degrees C. above normal, with the highest departures from normal centered over Quebec.
GFS model ensemble temperature anomaly forecast for Monday in degrees F.
My look at the overall pattern across Canada for this week.
Some forecast model clues through the end of August and an update on global sea surface temperatures.
Tornado threat into Tuesday from southeastern Saskatchewan to northwest Ontario.
Latest weekly clues to the long range forecast through mid-August.
Major storm for the Prairies early next week could bring heavy rainfall and severe thunderstorms.
Severe thunderstorm threat later Thursday and a general look at the upcoming weather pattern.