Brett Anderson

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Major Cooling on the Way and Gabrielle Update

September 10, 2013; 10:16 PM ET

You can also follow me on my twitter for updates....@BrettAWX

Fall now in its full glory in the north country

A nice webcam image from Tuesday afternoon showing brilliant, peak fall colors near Fort Yukon, Alaska.

A lot to talk about today....

A big cluster of thunderstorms along a warm front tracked southeastward earlier this morning from the Lake Huron region to upstate New York.

The brunt of the storms tracked from the Gravenhurst, Ontario, area to the Peterborough and Belleville region.

During a 5-hour period from 3 a.m. to 8 a.m. Tuesday, there were over 15,000 lightning strikes with this complex. See image below.

Behind the thunderstorm complex, heat and humidity blasted in with afternoon temperatures in the 33- to 34-degree C. range, but feeling more like 37 C.

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Strong thunderstorms Wednesday afternoon

Strong thunderstorms will likely erupt well ahead of a front Wednesday afternoon from the Saint Lawrence Valley to southwestern Ontario, including the GTA. Hot, humid air coupled with strong winds aloft will aid in the thunderstorm development.

The main window for severe thunderstorms with damaging winds in this region looks to be between 3 p.m. and 8 p.m.

More thunderstorms Thursday ahead of strong cold front

The leading edge of much cooler air (almost October-like) will trigger another round of potentially severe thunderstorms Thursday afternoon and evening.

This time, the main threat for Canada will be from northern New Brunswick through southern Quebec and possibly the Kingston, Ontario, area during the afternoon. The main threats with these storms will be damaging winds and hail. The worst of the storms will be from New England to the Middle Atlantic region by the evening.

Big cooldown coming!

Wednesday will be another scorcher before the thunderstorms hit across eastern Canada then cooling down for Thursday before the main shot of cool air arrives Thursday night and Friday. Afternoon temperatures across southern Ontario and southern Quebec will only hover in the 12- to 15-degree C. range!

There should be enough clouds and wind to prevent a widespread frost for the Saint Lawrence Valley and much of southern Ontario Friday night.

Gabrielle likely headed for Atlantic Canada

Tropical Storm Gabrielle which will be moving over Bermuda this evening will likely be drawn north then northeastward ahead of the strong cold front later this week.

The energy associated with this front may actually cause Gabrielle to strengthen a bit on Friday as it accelerates toward Cape Breton then Newfoundland.

At this point, it looks like tropical storm force winds could impact Cape Breton then the south coast of Newfoundland late Friday and Friday night.

Most of the strong winds will be east of the center track with a southeast to south direction.

The heaviest rainfall, likely 25-50 mm, will run along and just west of the track up through eastern Nova Scotia and western Newfoundland. The increasing forward speed of the system will prevent this from being a major flood maker.

This will be a quick-hitting storm (6 hours max) for most. The main impacts will be with the fishing fleet off Newfoundland.

There could be some minor tree damage and power outages to the east of the center track Friday night with possible southeast to south wind gusts in the 90-100 km/h range.

The Halifax, NS, area may get some rain out of this, but that is about it.

Gabrielle will lose tropical characteristics by early Saturday as it moves away from Newfoundland. Much cooler air will wrap in behind Gabrielle through the weekend.

West

Strong ridge of high pressure could produce near-record heat over southern BC Wednesday afternoon before cooler temperatures return.

Early next week it looks like unseasonably warm air returns to the western Prairies while a storm could bring widespread showers and thunderstorms to southern BC, including the Rockies.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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Brett Anderson
Brett Anderson covers both short-term and long-term weather and storm forecasts for Canada in this blog for AccuWeather.com.