Brett Anderson

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Severe Thunderstorm and Heavy Rainfall Potential

June 11, 2013; 3:17 PM ET

Thunderstorm Threat Wednesday afternoon/evening for parts of Alberta and Saskatchewan

Strong upper-level low over British Columbia will move very little through Wednesday. Ahead of this upper low, there will be an increasing southwesterly flow aloft into Alberta and Saskatchewan, while closer to the surface there will be an increasingly moist, southeast upslope flow.

At this point, it appears that the greatest threat of isolated, severe thunderstorms with hail and gusty winds will be across southeastern Alberta and extreme southwestern Saskatchewan. There is also just enough wind shear that we cannot rule out a tornado.


Heavy rainfall and thunder across southwestern Ontario Wednesday night

The combination of a strong upper-level feature in the area and the fact that there will be a sharp front dividing very hot and humid air over the Ohio Valley from the cooler air over Ontario will be a recipe for heavy rainfall and embedded thunderstorms for parts of southwestern Ontario, especially Wednesday night into Thursday morning.

I believe the main threat for severe, damaging thunderstorms will be from Ohio and Pennsylvania on south, but there still could be some very heavy downpours, gusty winds and vigorous lightning across extreme southern Ontario.

If there are going to be severe thunderstorms, they will most likely occur Wednesday evening near the Windsor/St. Thomas region.

Farther north and east, it looks like a period of heavy rainfall and thunder with the potential for over 50 mm of rain, especially from London, Ontario, on south. It appears that the northern edge of 25 mm or more will be just north of London then somewhere between Hamilton and the Niagara region.

Looks like the GTA will be on the northern edge of the rain late Wednesday night/early Thursday but you may see plenty of lightning flashes to the south.


I will be heading to the Cedar Point, Ohio, on Wednesday to check out the newest coaster Gatekeeper and ride my all-time favorite Millennium Force. The weather looks iffy Wednesday p.m. with scattered, strong thunderstorms, so I need to get a poncho on my way home this evening. Hopefully the deluge comes mostly in the overnight hours and moves out in time for Thursday's opening. I will be back in the office Friday.

The only good thing about this forecast for Cedar Point is that it should reduce the crowds and lines. Let's hope!

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


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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