After mild month, chaotic winter in the forecast
Wednesday may have brought a winter wonderland narrated by swearing drivers, but the month of November is shaping up to be about three degrees warmer than normal.
That's considered to be quite something, said David Phillips, Environment Canada senior climatologist. The only other Novembers like it on record were in 1948 and 2011.
And after that? Get ready for an unsettled winter, jumping from one weather event to the next.
“It's like weather wars,” said Phillips. “You'll get a little of this, and a little of that. It's like a winter with multiple personalities.”
The reason is La Niña, the cooling of the ocean surface temperatures in the Pacific Ocean. The World Meteorological Organization announced in September that La Niña has developed and is expected to last into next year, affecting temperatures, precipitation and storm patterns.
“It's not just a little episode. It's moderate and supposed to grow,” said Phillips. “Sea surface temperatures are one degree below normal. It's quite extensive and it has an effect on weather patterns in North America and around the world.”
For Ottawa, factors like the polar vortex and warm air from the Southern U.S. come into play.
The risk of this kind of winter is more freezing rain than normal — and freezing rain is always a risk in the Ottawa Valley, said Phillips.
“It really is a mixed bag. It tends to be wetter than normal. But it doesn't necessarily mean more snow. It can mean more rain,” he said. “It tends to be a sloppy, slick kind of winter. Not a lot of snow will stay on the ground.”
There were 14 La Niña winters between the 1950s and 1980s, and 10 were colder than normal and five were warmer than normal, said Phillips. In the past 30 years, there were 10 La Niña winters, and six were warmer and four were colder.
Environment Canada won't release its long-range winter forecast until Dec. 1, but the forecast for December is for weather that is warmer and more dry than normal.
As for other weather prognosticators, the Canadian Farmers' Almanac predicts near-normal temperatures will predominate across Quebec west to central Ontario.
The Old Farmers' Almanac says winter for the southern Quebec region, which includes Ottawa, will be colder than normal, on average, with much above-normal precipitation and snowfall.