Prairie Weather (Rural Roots Canada) – El Niño is building. Does that mean a warm, dry winter for the Prairies?

El Niño is building toward potentially historic strength. For Western Canada, that usually raises the prospect of a warmer, drier-than-normal winter.

So, are we in for a winter with less snow, fewer prolonged cold spells and another challenge for Prairie soil moisture?

Not so fast.

It is true that El Niño conditions typically produce warmer, drier conditions across the Canadian Prairies in winter, and cooler conditions in Eastern Canada. That has been well advertised over the past few weeks and months. And indeed, the latest model data continues to suggest it will be warm and dry across the Prairies. And not just across the prairies, either. This El Niño could be so powerful that it warms the entire country.

The map below shows the probability of above-average temperatures across Canada in December, January, and February. Note that the lowest probability is in southeastern Alberta:

And here is the chart for the same time period, showing a probability of below-average precipitation for Alberta, parts of Saskatchewan, and the northern Interlake in Manitoba:

Looking at the two maps above, one would assume this winter will be warm and dry across the prairies.

Again, not so fast.

Let’s check another outlook, this one from the European Centre for Medium-Range Weather Forecasts.

Like the Canadian outlook, this one also shows the warm El Niño influence extending across Canada.

Here’s the precipitation outlook from ECMWF:

The European outlook suggests an even drier pattern for the prairies and, like the Canadian outlook, shows Alberta as potentially the driest region in the country.

It would be easy to stop there and conclude that we’re in for a warm, dry winter.

But there’s something else in play that’s not getting talked about a lot. Something that could turn this weather outlook into a big, embarrassing bust.

The Pacific Decadal Oscillation.

Before your eyes glaze over, here’s an explanation:

El Niño refers to the pattern of changing Ocean temperatures off the coast of Peru. The Pacific Decadal Oscillation (PDO) refers to a pattern of changing ocean temperatures in the North Pacific Ocean, off the west coast of North America.

Historically, major El Niño events, the kind that give us warm, dry weather, occurred during a phase in which the North Pacific temperatures were colder than average. This year, they’re warmer than average in the central and western North Pacific, but colder than average along the west coast of North America.

This may dampen some of the typical El Niño effects, perhaps weakening the warmth and modifying the drying effect.

El Niño can favour milder winter conditions across the Prairies, but it doesn’t guarantee an exceptionally mild or low-snow winter.

For producers, the distinction between temperature and precipitation is important.

A mild winter can reduce the duration of extreme cold, but it doesn’t necessarily mean good growing conditions the following spring. Precipitation falling as snow, snow accumulation, spring rainfall and the timing of melt all influence soil moisture heading into seeding.

Likewise, a winter with below-normal precipitation doesn’t automatically mean drought next summer. Spring and summer weather will still play a major role.

For now, the seasonal outlooks provide a reasonable starting point. They suggest that warmer-than-normal conditions are favoured, with a potentially dry winter across parts of the Prairies.

But it’s not necessarily a done deal.

This is a particularly strong El Niño, and the interaction between tropical Pacific warming, the North Pacific and the atmosphere is worth watching closely. We should be cautious about assuming that the historical relationship will translate directly into this winter’s weather.

The coming months will tell us more.

For Prairie producers, the practical takeaway is simple: keep an eye on the seasonal outlooks, but don’t make assumptions about next spring’s soil moisture just yet.

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