Winter will come in like a lamb and go out like a lion, according to AccuWeather.
December is expected to be warmer and windier than normal because of several Pacific systems from British Columbia sweeping across the region with strong jet streams.
“As we get into January and February, we think the pattern is going to change,” said senior meteorologist Brett Anderson.
A “mini-blob” of warm water in the northeast Pacific Ocean will create a high pressure system that will push a series of Arctic blasts south.
“It opens the door to these cold intrusions down into the Prairies,” he said. “It’s certainly going to feel colder than last winter, which was fairly mild across basically all of Canada.”
Cold Arctic air doesn’t contain much moisture, so it will be drier than normal in Manitoba, Saskatchewan and parts of eastern Alberta.
Western Alberta should have normal snowfall because the mountains and foothills cause the Arctic air to rise.
Drew Lerner, president of World Weather Inc., agrees there will be a cooler trend because of the recent plunge into the negative phase of the Arctic Oscillation climate pattern.
“Any time you get a significant fall into negative Arctic Oscillation at this time of year, it is not something you recover from,” he said.
It means the Prairies will be exposed to Arctic air blasts.
“So we will progressively cool as we go through the autumn and into the winter,” said Lerner.
“The only reason why we’re not notably cold right now is that the whole Northern Hemisphere is still recovering from the El Nino heat.”
That lingering heat should create windows of opportunity for farmers to finish harvest in most areas of the Prairies, although that is unlikely in the really wet areas such as northeastern Saskatchewan and northwestern Manitoba.
The negative phase of the Arctic Oscillation typically lasts three months but can stick around for up to six months.
He believes the colder than normal weather could stay around through February because of the influence of a weak La Nina forming this fall or early winter.
Lerner does not agree with AccuWeather’s forecast for a warmer than normal December or for a drier winter for much of the region.
La Nina years tend to produce above average precipitation in western and southern Alberta and southern Saskatchewan.
He believes it will be dry in Manitoba and northeastern Saskatchewan, normal for the remainder of Saskatchewan and above average precipitation in western and southern Alberta.
Anderson said the caveat in his forecast is climate change.
“It’s tougher to get these colder winters nowadays, but they’re going to happen from time to time and this year is one of the setups we think will do it,” he said.
There are too many supporting factors, such as the La Nina favouring Arctic air masses descending across the Prairies.
Another factor pointing to a cold winter are the analogs of this year’s weather to date, which suggest a winter similar to 2013-14, which was miserable.
And then there is Siberia’s snowfall. When Siberia receives higher than average snowfall in October, it favours a high pressure system setting up over the North Pole in mid-winter, pushing cold air south. That is the case this October.