As the holidays approach, a pattern change is ahead

Monday, December 19, 2016, 5:53 PM - December has featured an abrupt transition to winter all across Canada.

WINTER IS HERE: With La Niña helping shape global patterns what will Canadians expect from winter? Find out with The Weather Network’s 2016 Winter Forecast | FORECAST & MAPS HERE

Often when one side of the country is cold, the other side is mild, but over the past week nearly all of Canada has experienced well below seasonal temperatures. 

The image below shows temperature anomalies (departure from normal) for the past 10 days. The coldest weather relative to normal is highlighted by the various shades of purple/violet which represent temperatures 10 to 18ºC below normal.

This is in in stark contrast to the dominant pattern that we saw for much of the fall season, especially throughout November, which in many places was the warmest on record.

The image below shows temperature anomalies (departure from normal) across Canada for November. The various shades of orange and red highlight that nearly the entire country was warmer than normal.

Many people are now asking if winter is here to stay, or will there be relief from the frigid temperatures for the Holidays? Here’s the latest on the long range forecast trends.

Fortunately for those who already have an early case of winter fatigue, the highly amplified jet stream pattern responsible for the recent rounds of Arctic air has run its course (for now). A more zonal pattern will dominate the rest of this week, allowing above-normal temperatures to spread from west to east across most of Canada before Christmas.

The image below shows forecast temperature anomalies for December 20-25. Above-seasonal temperatures are expected to stretch from east of the Rockies to Atlantic Canada, with the core of the "warmth" from the eastern Prairies to the Great Lakes. Meanwhile, chilly temperatures will linger longer for Newfoundland and Labrador. In B.C., a break from the frigid arctic air arrives, but temperatures will remain cold enough for ski areas to continue to build snowpack.

While this map may look rather spring-like for many areas, it is important to keep in mind that "normal" temperatures are now cold enough that it’s quite possible to get snow and ice with near to above normal temperatures. During Christmas Day, a strong Colorado Low will approach the Great Lakes, and have a significant impact on travel from Manitoba to Southern Quebec Christmas night and Boxing Day. The image on the left shows a model forecast for Christmas evening and night while the image on the right is for Boxing Day morning. Please check back later this week for a more extensive discussion on the impacts of this powerful system.

Behind this storm, a quick shot of colder weather is expected in the Great Lakes. However, a milder pattern is expected to quick return. The map below shows the dominant weather pattern that we expect during the final days of December and into the first half of January 2017. While western Canada will once again have to contend with rounds of arctic air, much of central and eastern Canada will see a few weeks in which near to above seasonal temperatures will dominate.

While central and eastern Canada can expect a break from persistent arctic outbreaks, this is by no means the end of winter. We expect that there will be another significant pattern change during mid-January which will bring another extended period of below seasonal temperatures for these regions.