Pattern reversal to follow exceptionally warm October day

Tuesday, October 18, 2016, 8:30 PM - "Feels like" isn't often a term you hear in mid October, but thanks to a warm sector from Monday's system, Southern Ontario saw a taste of summer on Tuesday.

A much-appreciated warm spell crept into the forecast after damaging storms -- including one confirmed tornado -- lashed the region Monday. However, a late-week cool down precedes a pattern reversal early next week, which will see below-seasonal temperatures for many. More on that, below.

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Severe thunderstorm watches and warnings dropped Monday evening after storms pummeled areas near the Georgian Bay with damaging winds, causing power outages to 40,000 customers.

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"Several reports of wind damage from the Collingwood and Stayner areas were received," Environment Canada said in a weather summary. "Uprooted trees, a removed roof, and flipped trailers were reported."

The weather agency sent a damage survey team to the area on Tuesday, confirming that one tornado has lashed the Stayner area. The EF-scale rating has yet to be determined.

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Areas north of Lake Superior are forecast to see as much as 40 mm of rain through Tuesday, with residents near the Georgian Bay area to have seen up to 25 mm.

Warm sector over southern Ontario

Temperatures felt like the 30s on Tuesday, causing some to refer to the warm spell as "hotober."

Toronto's daytime high of 25^oC, felt like 31 with the humidity by Tuesday afternoon. 

Interestingly, only two days have reached 30 C or greater in the month of October since records began at Toronto Pearson in 1937.

Thunderstorm risk

A strong cold front that pushes through southern Ontario Tuesday brings the risk for some isolated thunderstorms through the evening.

"Instability parameters aren't overly impressive, but the wind shear in place is rather high," says Weather Network meteorologist Brad Rousseau. "IF the storms form in time over the western edge of the risk area, they will likely be able to mature in time, which will bring the slight chance for some of these storms to reach severe criteria mainly in terms of strong winds."

Environment Canada issued a series of Special Weather Statements Tuesday evening in advance of the cold front.

"A line of showers and the odd thunderstorm will pass through the area [Tuesday] evening ahead of a cold front," the agency said. "Brief wind gusts to 70 or 80 km/h are possible with these showers."

Winds are expected to quickly diminish as the cold front passes through.

While there will be a slight risk for a few severe storms across the entire risk area, the highest potential will be for southeastern Ontario into southeastern Quebec.

Thursday is looking like another wet and stormy day for southern Ontario as gulf moisture funnels up the Ohio Valley into the region, resulting in generally 15-20 mm over the extent of the day.

Cooler temperatures spread into the region behind the system with temperatures struggling to reach double digit values by Friday. 

Pattern reversal brings blast of cooler weather

So far October has featured well above seasonal temperatures from the Great Lakes to the Maritimes with an early start to winter felt across much of the Prairies.

"By early next week however, the Great Lakes to the Maritimes will be below seasonal while Western Canada will be closer to seasonal," says Weather Network meteorologist Dr. Doug Gillham. "For southern Ontario and southern Quebec, this will likely be the longest period of near to below seasonal temperatures that we have seen since spring as our cool downs this summer and fall (so far) have generally just taken us to near seasonal for a couple of days."