Monday, December 16, 2024

No real rain breaks with stalled and retrograding low over Atlantic Canada

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An extended period of wet and windy weather is likely over Atlantic Canada due to an atmospheric gridlock with a strong blocking pattern over the North Atlantic Ocean. This will be followed by a retrograding low, essentially reversing direction, and keeping the stormy conditions moving back westwards.

Brace for heavy rain and powerful winds as a result of the back-to-back storms, with localized flooding and power outages threatening parts of the region through the week. A temperature rollercoaster could also bring some localized mixed wintry precipitation to higher terrain, with some icy travel and the risk for accumulating snow.

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More winds and rain in an extended soggy pattern

A strong high pressure system off the coast of Europe is going to prevent systems from tracking through Atlantic Canada this week, and instead will have them lingering over the region for days on end.

Baron - ATL Wednesday pressure tracker

Baron – ATL Wednesday pressure tracker

After a milder and wet start to the week on Monday, a second system will track in on Tuesday, bringing rain to the Maritimes, and even some localized mixed precipitation and snow to some higher terrain as temperatures fall.

The system then pushes into Newfoundland, stalling out just south of the Avalon Peninsula. The system will be wedged between the high off the coast of Europe, and an incoming high pressure system from Ontario and Quebec.

This pattern sets up a boundary over central and eastern Newfoundland, which will bring persistent heavy rain from Tuesday night through Thursday. Current forecast models suggest that 50-100+ mm of rain could fall during this time period.

Baron - ATL rain totals - Nov12Baron - ATL rain totals - Nov12

Baron – ATL rain totals – Nov12

“Localized flooding in low-lying areas is possible,” says Environment and Climate Change Canada (ECCC) in the rainfall warning issued for the Avalon. “If visibility is reduced while driving, turn on your lights and maintain a safe following distance.”

Threat for outages

At the same time, winds will also increase drastically over Atlantic Canada, gusting between 70-90 km/h, and even higher along exposed coastlines.

Baron - ATL Wednesday evening windsBaron - ATL Wednesday evening winds

Baron – ATL Wednesday evening winds

The combination of strong winds and heavy rain could lead to power outages across the harder-hit areas.

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The low then retrogrades as high pressure forces it back west over top of the Maritimes, bringing more rain to eastern regions to end the week.

Baron - ATL Friday morning precipBaron - ATL Friday morning precip

Baron – ATL Friday morning precip

Meanwhile, parts of central and western New Brunswick will face some wintry weather, and the potential for slick and icy conditions, as well as accumulating snow.

This precipitation moves back into the Maritimes on Friday once again, and continues through Saturday before finally tracking north through Quebec.

There is less confidence in how the system will react late week, so it’ll be important to stay up-to-date on the forecast and any weather warnings issued in your area.

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