Sharp cool-down, unsettled conditions for southern Ontario
Wednesday, March 22, 2017, 10:06 AM - After a mild start to the week in southern Ontario, a shot of Arctic air has brought a drastic cooldown to the south of the province, with Wednesday morning feeling more like midwinter than early spring.
The frigid air mass won’t linger long, but by Friday, a complex weather pattern develops which will mean an extended period of unsettled conditions and sharp temperature contrasts, as well as a threat for wintry weather for some.
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Tuesday afternoon saw widespread high temperatures in the double digits across southern Ontario, but an approaching Arctic front is sent temperatures plunging overnight into Wednesday morning, made worse by gusty northwest winds.
Wednesday’s high temperatures will remain in negative territory for most, with only Windsor threatening to break the freezing mark. Gusty winds continue through the day, which will make conditions feel even more miserable.
Milder, but still below seasonal temperatures return for Thursday, ahead of a developing weather system which will mean unsettled weather and a challenging forecast for Friday into the weekend.
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Early Friday will see precipitation return to the region, as moisture spreads north ahead of an advancing warm front. Many locations across southern Ontario will remain warm enough start out as rain on Friday, but colder spots may start out with a period of snow or mixed precipitation, before the arrival of warmer air allows a changeover to rain.
Late Friday into the weekend, the forecast will become increasingly more challenging, a slow-moving pattern allows the front to linger over the region. A pair of stout high pressure centers, one located over northern Ontario and the other over the Atlantic, will help to keep this boundary fixed in place over southern Ontario for an extended period of time.
Cold northeasterly flow to the north of the boundary, and mild southwesterly flow to the south will set up a zone of sharp temperature contrast across the region. Meanwhile moist air surging northward ahead of a developing weather system in the central U.S. will overrun the front, leading to an extended period of precipitation.
The sharp temperature contrasts and long duration of precipitation will make this weekend’s precipitation type forecast particularly difficult, and some locations may see back-and-forth periods of rain, snow, and mixed precipitation through the weekend.
We are increasingly concerned that a significant period of freezing rain will develop for the region later in the weekend. This would lead to more disruptive impacts, including major travel complications. This forecast will continue to be refined as the event approaches, but now is the time to start paying close attention to the weekend forecast, particularly if you have travel or other weather-sensitive plans.
Check back for updates as The Weather Network continues to monitor these systems.