A surge of warm and somewhat humid air will cover most of southwestern Ontario Tuesday with afternoon temperature in the 26-29 C range. The exception will be near the lakeshores, where the cold water will lead to much cooler breezes.
The combination of high temperatures, increasing dewpoints and cooling aloft will lead to some thunderstorms during the day and evening Tuesday with the potential for some heavy downpours.
A strengthening upper-level storm will send more energy into the high dewpoint air mass over southern Ontario Wednesday night through Thursday night with the potential for another round of heavier rain and strong thunderstorms. Flash flooding is a possibility during the period.
ECMWF model weekly update
The latest update of the ECMWF model seasonal forecast indicates a cool, somewhat wet summer for the central Prairies. We (AccuWeather) agree with the cool idea, especially from the central Prairies and farther east, but we are not as wet over the central Prairies.
The ECMWF continues to insist that a moderate to strong El Nino will be underway by the upcoming fall.
Based on the above information, the model forecasts drier-than-normal conditions over the Caribbean during the height of the tropical cyclone season and a below-normal number of cyclones in the Atlantic basin, which is in line with our forecast.
A moderate to strong El Nino would also support a milder winter in terms of temperatures from BC to the southern Prairies.
Farther east, the strength of El Nino is critical to the actual impacts, if any, during the winter.
If we do reach moderate to strong El Nino conditions by the last few months of the year, I would not be at all surprised if 2015 ends up as the warmest year on record globally.
A warm first half of summer for a majority of Canada.
Fast, west-to-east jet stream pattern across southern Canada into next week.
Clues to the long range over the next several weeks across North America.
Potential for significant rainfall over southwestern Alberta late this week into the early weekend.
A strong, upper-level storm system will bring significant rain, severe thunderstorms and much cooler air to parts of western and central Canada into early next week.
Latest ideas on the weekly long range through the end of this month.