Strong thunderstorms Thursday - much cooler weekend ahead

A cold front will produce widespread shower and thunderstorm activity across eastern Ontario and southern Quebec on Thursday. Some of the storms may be on the strong side, especially across eastern Ontario, with heavy rain, hail and high winds possible. There is even a risk of an isolated tornado in Ontario.

Active weather continues across many regions of Canada this week, perhaps with the exception of southern Quebec, at least for now. Cloud cover from a decaying area of thunderstorms in Ontario, is limiting the sunshine across southern Quebec Wednesday morning. Montreal is muggy and on the warm side, but not as warm as expected due to the cloud cover. Expect some breaks this afternoon, with an optimistic high of 27C (81F). Tonight will be muggy, with lows remaining in the upper teens to near 20C. Thursday will see a high once again of 27C.

A steamy airmass is located across the midwestern US Wednesday, nudging into southwestern Ontario. Widespread heat warnings are posted today, including across extreme southwestern Ontario where temperatures are expected to soar into the middle 30s, with humidex readings over 40C. This same airmass was the trigger for widespread severe thunderstorms late Monday and Tuesday. The storms produced wild lightning, strong wind gusts in excess of 120km/h and hail. Power outages and damage was observed from Michigan into portions of Ontario and south across Indiana and Ohio.

On Thursday, warm and humid air will settle across eastern Ontario and southern Quebec. By mid-afternoon, strong thunderstorms are forecast to develop along a potent cold front in central Ontario, moving southeast into the St. Lawrence Valley. At this time, the bulk of the storms should remain southwest of Montreal, clipping the Valleyfield area in the afternoon. A few isolated cells may make it into the metro region. Heavy rain, strong wind gusts and hail will be the main threat. I will update the potential for severe weather in Montreal early Thursday morning.

A childhood friend of mine sent this photo of heavy wet snow, taken Tuesday, June 14 in Elk Valley, BC. The snow fell from a strong storm system moving east across Montana and into Alberta and Saskatchewan. The storm produced heavy rain and snow, with flooding reported in parts of Alberta south into Montana and Wyoming.
Photo: Elizabeth Jones

While warm weather prevails in the east, a strong winter-like storm moved across western Canada. Strong winds occurred across southern Alberta and Saskatchewan, along with extremely heavy rainfall and in some cases heavy wet snow. Calgary reported over 50mm of rain, with localized amounts exceeding 100mm. Heavy rain and flooding also impacted parts of Saskatchewan, with as much as 100mm falling in the Battlefords. A childhood friend of mine living in the Elk Valley in southeastern British Columbia sent me a picture of heavy snowfall which fell late Monday into Tuesday morning. The storm in question is weakening across the Prairies on Wednesday.