A big-picture look at why this winter was so unusually warm

An ongoing battle between a western ridge and eastern trough explains why Alberta has been warmer than average for so long

No matter which way you look at it, winter is over across agricultural Alberta — and it was definitely a warm one.

While it won’t go down in the record books, Alberta’s been in a persistently long warm spell with seven consecutive months of above-average temperatures recorded at all three of the main locations.

Winter is typically defined as the time period that runs from December to the end of February, but I feel for our part of the world that winter is really November to the end of March, or what I call “extended winter.” When I looked at the temperature departure from average at all three locations (Calgary, Edmonton, and Peace River) for this time frame, the values all came in very close to one another. Both Calgary and Edmonton recorded an extended winter temperature that was 2.8 C above average, with the Peace River region coming in 3.0 C above average.

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April, so far, has started out with extremely warm temperatures as a persistent ridge of high pressure has dominated the province. It is kind of tough for me to write about these types of weather events because the time lag between my writing deadline and when you read this is more than a week. So by the time you read this the weather stories can already be old news. The early-April heat wave, for example, may have already given way to a cold snap by the time you read this. Fortunately, this doesn’t look to be the case.

Here is the big picture of what is going on with the weather across much of Canada along with the northern and central U.S.

Looking at the current large-scale weather pattern, there has been a fairly persistent ridge of high pressure over western regions, with the centre of it fluctuating back and forth between Alberta and the B.C. coast. A large trough of low pressure has been sitting over eastern regions that is associated with the polar vortex that has been rotating around Baffin Island. This has allowed for mild conditions to develop under the ridge of high pressure, and cold air to work its way south in the trough of low pressure. We have seen our share of the western ridge this winter, which is what brought all the warm weather.

As these two main features undergo strengthening and weakening, our resulting weather changes. The strengthening and weakening of these two systems does not necessarily have to go hand in hand. For example, if the western ridge strengthens, this doesn’t mean that the eastern trough will weaken. A strengthening of the western ridge will bring drier and warmer weather over western regions, with the warm air often pushing farther east. A strengthening trough over eastern regions will see colder air pushing farther south and often we’ll see an accompanied westward push of colder air. If one of these features strengthens while the other one weakens, then we’ll see that feature take over the overall pattern. If they both weaken, then average conditions tend to dominate across much of Canada.

What has happened during the first week or two of April is a strengthening of both of these features. This has led to the development of some remarkable west-east temperature contrasts. For example, on April 3, temperatures across Alberta were topping out in the 21 to 25 C range (with southwestern and south-central Saskatchewan having similar, if slightly cooler, temperatures). Across southeastern Saskatchewan, temperatures struggled to make it to 10 C for highs, while in southern Manitoba, temperatures in the Winnipeg region had a hard time making it to -5 C! That’s nearly a 40 C temperature difference, which is not that unusual going from north to south, but is fairly unusual in this west to east configuration.

The question (that if you knew the answer to, would be worth millions) is whether or not this pattern will continue into the foreseeable future?

Well, I’m not walking around with a tonne of money, but I’ll still give the answer a shot. The current medium-range models are showing this pattern staying in place until around the middle of April. They then show both of these features weakening significantly.

This in itself is not unusual as they have been strengthening and weakening all winter long. The big question is whether or not one or both of these features will strengthen again, or will a different weather pattern take shape and dominate the rest of spring and early summer?

I wish I knew the answer, but my best guess is that we’ll continue to see the western ridge trying to re-establish itself, while the eastern trough weakens as we move closer and closer to summer. This would mean a better-than-average chance of seeing a continuation of warmer and drier-than-average conditions for spring and early summer. Guess we’ll just have to wait and see.

About the author

AF Contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the University of Winnipeg. He operates a computerized weather station near Birds Hill Park, Manitoba.

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