'Disruptive' winter storm spans 50% of the country: Timing

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Erin Wenckstern

Meteorologist

Wednesday, January 10, 2018, 9:28 AM - The first attempt at a blissful January thaw will come to a crashing and hectic end as a major winter storm takes aim at eastern Canada, from southern Ontario to Atlantic Canada late this week. Hardest hit areas will be digging out of 20-30+ cm of snow, with some threatened by significant freezing rain and possible power outages.

While the storm is too far out to discuss the details for specific locations, we know the system will be unlike any storm we've seen so far this season. How? It's all in the atmospheric set up.

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This week, relatively "balmy" temperatures will treat eastern Canada to a much appreciated break from frigid air. In fact, daytime highs may possibly flirt with double-digits for some Thursday and Friday. But, don't be fooled: the surge of mild and moist air from the southern U.S. will deceptively be setting the stage for our winter storm.

Throughout this brief intermission from winter, a potent piece of energy (a crude description of upper level atmospheric spin) will race across the U.S. and fuel the development of a rapidly-strengthening low pressure system near the Alabama/Mississippi border. As an interesting aside, winter storms that develop in this region are notorious for bringing impressive snowfall to southern Ontario, since such storms bring abundant Gulf moisture with a storm track that draws Arctic air into the region.

As the low deepens, it will track up the Appalachians and then south of the lower Great Lakes. Meanwhile, an Arctic front will be pressing south across eastern Canada and the clash between the warm, humid air from the Gulf and Arctic air surging south will lead to a highly disruptive outcome: a swath of very heavy snowfall and a band of substantial ice (pellets & freezing rain) across parts of southern Ontario, Quebec and the Maritimes. How far south that Arctic front sinks and the exact track of the low will play key roles in determining who will see the biggest impacts from this storm; details that will be fine-tuned in the days to come.

What we know: Timing and likely impacts

Thursday

An initial system kicks off the entire show as it passes across northern Ontario. Widespread snowfall, potentially heavy at times, Wednesday overnight through Thursday is expected. Gusty northeast winds may also result in areas of blowing snow.

Across southern/central Ontario and into southern Quebec, temperatures will soar well above the freezing mark, leading to periods of rain across the region on Thursday. The combination of mild air and rain will rapidly erode our current snow pack, potentially raising the risk of localized flooding should the rain become heavier. On top of that, the warmer air constantly overrunning the depleting snow pack will create ripe conditions for thick fog to develop. Travel may be impacted with poor visibility.

Friday

As the first system continues on its eastward track Friday across the Maritimes, the Arctic front will begin its southern migration into southern Ontario and Quebec.

As a result, conditions will deteriorate from north to south as the front descends, causing periods of rain to change to ice and snow for many throughout Friday. Travel across eastern Canada looks to become increasingly impacted during the day.

Friday Overnight - Saturday

With the Arctic front now draped over southern Ontario through New Brunswick, our approaching storm from the south will run into this stubborn boundary. Widespread snow will re-develop Friday night into Saturday, with the threat for a swath of freezing rain to the south. Again, hardest hit areas could see upwards of 20-30+ cm from this storm and areas with significant freezing rain run the risk of power outages.

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Sunday

A fresh blast of Arctic air takes over from the west to the east, putting our January thaw on a hiatus -- not an end -- for several days.

"A more extended January thaw is on the way later next week," says The Weather Network meteorologist Dr. Doug Gillham. "But I’m starting to question the duration of the thaw – some signs that the return to winter will be quicker than I expected."

In conclusion, whether this becomes a significant snow or ice threat for your area, travel across eastern Canada and the northeast U.S. will be highly impacted and it's good to keep an eye on this developing storm.

Check back for updates as we fine-tune the details of this forecast.

Watch below: DARING divers go below ice to explore Tobermory wreckage