Eastern thunderstorms into tonight
The leading edge of much warmer, more humid air will be pushing across southern Ontario later this evening and overnight. This will likely lead to widespread thunderstorms and locally heavy rainfall across the region as the cluster of storms tracks eastward. While the severe threat is low, these will be the type of storms that dump a significant amount of rain over a couple of hours with plenty of lightning. Localized amounts of 50 mm or more (especially from Kitchener on south/southwest) are certainly possible where cells concentrate through tonight.
By tomorrow (Wednesday), a disturbance coming around from the northwest could trigger a band of locally severe thunderstorms (though not nearly as widespread as tonight) across eastern Ontario and into upstate New York with the potential for wind damage.
I will try to get some maps up later in the day.
Heavy rainfall for the Prairies
A large, slow-moving storm system will track northeastward into the southern Prairies Wednesday night through Friday, bringing another round of significant rainfall to the region.
At this point, it appears that the heaviest rainfall will run from extreme southeastern Alberta through southern Saskatchewan. In this region there is the potential for widespread rainfall amounts of 25-50 mm and locally 75 mm from Wednesday night through Friday.
Significant rainfall is also likely for extreme southern Manitoba with this system from Thursday through Friday with the potential for over 50 mm and even some thunderstorms.
My June outlook
Here is my own forecast for June in terms of temperature and rainfall departures from normal.
Forecast pattern clues through most of July.
Thunderstorms this weekend and a look at the long range.
Some new clues to the summer and fall season.
Amplified jet stream pattern will keep forecasters on their toes over the next week or so.
Weather pattern clues for the next several weeks.
A look back at May and the spring of 2016 in terms of temperature departures.