Heat wave probability tanks, Ontario and Quebec pattern
Monday, July 16, 2018, 2:13 PM - It's been hot. It's been sticky. And quite frankly, Chris Murphy eloquently said it best, "this humidity is akin to used bath water" -- it's uncomfortable and gross.
But as we enter the second half of July, the winds of change will whip through Ontario and Quebec, delivering a much more comfortable air mass and effectively knocking the probability of another heat wave down to near zero.
For an outlook on what the remainder of July holds for Ontario and Quebec, read on.
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In June and up to mid July, both provinces gained multiple heat warnings as humidex values peaked in the high 40s and up to 70 deaths were connected to Quebec's potent heat wave.
To understand why this happened and why we're in for a change, a quick peak at the upper atmospheric pattern reveals the culprit: a strong, rather persistent ridge in the jet stream loomed over the region. A ridge is a frequently used term in meteorology and simply put, it acts as a protective dome overhead, deflecting rain-bearing systems and enforcing dry, hot weather.
Going forward, the ridge will migrate westward and find a new home over the southwest U.S. for the remainder of the month. As this retrograde unfolds, the pattern allows weak disturbances to roll on the outer edge of the ridge, bringing a few rounds of unsettled weather and our once protective dome will now be busy deflecting systems into the Great Lakes. Looking at the animation below, the periodic blue zones highlight the progressive pattern of systems moving in, while the large red spanning the desert southwest depicts the migrated ridge.
When does it begin? It's already underway, but the first real signal that our atmosphere has changed comes in this weekend. A slow-moving low will approach the Great Lakes on Saturday, spreading into Quebec through Sunday and Monday with scattered showers and thunderstorms in the forecast and temperatures near seasonal.
CLICK TO PLAY: WEEKEND SYSTEM OVER ONTARIO AND QUEBEC
WILL IT BE COLD?
Hardly. This evolving atmospheric change means temperatures will return to more normal values, with a few days potentially below seasonal as opposed to consecutive humidex days in the 40s. A quick reminder that normal temperatures this time of year are typically in the 25°C to 27°C range. It seems unlikely, under this type of scenario, that a heat wave is in the cards.
HOW LONG DOES IT LAST?
Current indications suggest this type of "cooler" pattern will bring us through the rest of July and into early August. While there will be brief heat at times, the overall trend is for a return to normal temperatures as the ridge leaves us for the west.