What happened to Saturday's forecast in southern Ontario?

Friday, July 18, 2014, 1:06 PM - Our forecast for the upcoming weekend for the GTA has highlighted the threat for scattered showers and thunderstorms to interrupt an overall great looking weekend. I even said earlier this week on the Long Ranger segment on TV that I would give this weekend an 8 out of 10.

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However, it now looks like we will see a period of showers that will be more organized than we initially expected. Saturday will not be a total washout, but the day will be mostly cloudy and a period of showers will spread across the region. The additional cloud cover will also hold temperatures a few degrees below seasonal.

Sunday still looks to be on track to bring a mixture of sun and clouds and temperatures close to seasonal. While we still have the threat for scattered showers, most of the day will be rain-free.

Monday through Wednesday will be mostly sunny, very warm and humid with high temperatures rising to near 30 and a Humidex in the upper 30s. This certainly is not unusual for late July, but Toronto has not reached 30ºC during the month of July to the increase in heat and humidity will be noticeable contrast to the rest of the month.

While the timing is still uncertain, it looks like a cold front will approach the GTA late Wednesday. This will bring a period of rain and thunderstorms late Wednesday or Wednesday night into Thursday.

The end of next week and next weekend will bring a transition back to a cooler pattern. Forecast models typically do not handle the details and the timing of such changes very well, but there is good model agreement on where the pattern is headed for the final days of July and the first week of August.

The map below is a model depiction of the 10-day period from July 28 through August 6. The blue colors highlight the regions where temperatures are forecast to be 1 to 3 degrees below seasonal for that time period.

While this looks rather pessimistic, it does not mean that summer is over. Keep in mind that our average high temperature for this time of year is 27 ºC, so a slightly below seasonal temperature pattern can still bring many days of very pleasant weather to southern Ontario. We could even see a couple very warm days within that period, but overall it does appear that heat will not be the big story as we head towards the Civic Holiday long weekend.