Canada long range: Pattern changes on the way

Saturday, January 10, 2015, 8:13 PM - After a mild December across most of Canada, January has brought a return to a weather pattern that is reminiscent of what we saw during much of the winter of 2013-2014. Several round of arctic air that originated in Siberia have brought below seasonal temperatures to each province across Canada.

The image below shows the temperatures that we have seen so far during the month of January relative to average. The various shades of blue highlight the regions that have been 1 to 3 degrees colder than average while the various shades of green highlight regions that have had temperatures 3 to 7 degrees colder than average. The various shades of violet over parts of Saskatchewan, Alberta and British Columbia highlight places that have close to 10 degrees colder than seasonal for the beginning of January.

Looking ahead to next week, a pattern change will evolve as Pacific air rather than Arctic air will slowly spread across western Canada. While the week will start cold across the Prairies, temperatures will warm to above seasonal levels in Alberta by Tuesday and the milder air will spread into northwestern Ontario by the end of the week. Meanwhile, below seasonal temperatures will continue from the Great Lakes to Atlantic, but the pattern will not be quite as frigid as what we have seen at times during the past week.

We will also see a change in the storm track next week. The first week of January brought a series of clippers that have tracked across the continent, but next week we will be watching the development of two low pressure systems over the Southeastern United States.

The first low will track south of the Great Lakes during Sunday night and Monday, with the northern edge of the system bringing several centimetres of snow to parts of southern Ontario and southern Quebec. This low will strengthen as it tracks south of Nova Scotia and bring more significant snow (with the potential for mixed precipitation) to the southern Maritimes and southern Newfoundland.

There is considerable uncertainty regarding the track of the second system, but it certainly is a storm to watch for eastern Canada late next week as it will be the stronger of the two systems.

Most of next week will feature a quieter weather pattern across western Canada, but it looks like the end of next week and the following weekend will bring a return to a more active pattern for the south coast of British Columbia.

Getting back to the national temperature pattern, the milder Pacific air should make additional progress east as we head into the following weekend and beyond (January 17-24), with the potential for a January thaw from the Great Lakes to the Atlantic. However, this milder pattern is not expected to stay around nearly as long as it did during December.

It looks like January will end much like how it began with below seasonal temperatures returning for much of the country, and this pattern is expected to persist into February.