Alberto has been blamed for flash flooding, mudslides and power outages in parts of the Southern United States. The remnants of Alberto will churn into Michigan this evening – increasing humidity readings and creating unsettled conditions for Southern Ontario, beginning late this evening.
High dew-point values will envelop much of Southern Ontario Wednesday through Thursday. Overnight lows near or above 20C Wednesday night, coupled with dew-points in the high teens, will lead to stifling conditions in doors for residences without air-conditioning or central-air.
High humidity with temperatures in the middle to high teens will act as fuel for Thunderstorms Wednesday night in Southwestern Ontario – with a widespread risk for Thursday morning through evening for the rest of Southern Ontario.
The remnant low of Tropical Storm Alberto will act as a trigger Wednesday night and Thursday. As the remnant low approaches Michigan, bands of showers and thunderstorms will wrap around the low.
On Thursday, the low will coalesce will a cold front and get absorbed by the Jet-stream. Upper-level energy and a cold front is expected to act as a trigger for widespread thunderstorms, some of which could turn severe. The primary risk with any thunderstorms that develop Thursday will be torrential rainfall and gusty winds. We will be watching Southwestern Ontario where rainfall could be an issue with minor flooding concerns.
A secondary cold front passage is expected Friday – which may act as a trigger for another round of thunderstorms. Again, rainfall will be the primary concern. Small hail is also a possibility.
It’s important to note, the next couple days aren’t expected to be a wash-out for everyone. Some locales may only see a few millimetres of rain. Whereas other locales, who receive several rounds of thunderstorms or training thunderstorms, could see locally 50mm or more.
Some solace from the humidity is expected by Saturday. Temperatures return to normal with brilliant sunshine and no humidity.
A deep-layer of tropical moisture will move well north into Canada. Reaching as far North as James Bay and Northern Quebec. Heavy rainfall is expected along a boundary between Lake Superior and James Bay continuing into Northern Quebec. Totals rainfall amounts between 40-75mm are expected in the next 48 hours in the region.