Yellowknife (Mar 10/06) - Puzzled by the warm weather? So are the meteorologists.

From December to February, Canada experienced the warmest winter on record. Yellowknife is at ground zero.

The region from the Beaufort down through Great Slave Lake and into Northern Saskatchewan logged the biggest change anywhere in the country, with average temperatures rising more than seven degrees above normal for months.

Researchers with Environment Canada's Meteorological Service compared recent information with data dating back to 1948.

"I've seen warm and exceedingly warm (weather) over the Arctic in the winter, but I have never seen such a pattern," said Yvonne Bilan-Wallace, an Edmonton-based Warning Preparedness Meteorologist with Environment Canada. "The weather didn't set up as it normally would in the wintertime."

Traditionally, a winter vortex of cold air forms above the Arctic islands or in northwestern Nunavut, sucking cold air down across the NWT.

This year, slow-moving mild air travelled up the Pacific coast from Vancouver, pumping the warm air into the Mackenzie Valley.

"Why the vortex itself didn't set up and why this persistent pattern from the Pacific set up I don't know," Bilan-Wallace said. "To say it's unprecedented would not be exaggerating."

Weather patterns are affected by what's happening in the oceans, the atmosphere and the upper atmosphere above the weather zone. The absence of the cold Arctic vortex will affect weather patterns in Ontario, Manitoba and Saskatchewan.

"I can't find any excuses this year to say why this particular pattern happened," she said.

"Meteorology is like having to put together a puzzle with 100 pieces and telling what that picture is going to look like using only 15 pieces. Meteorologists and climatologists don't have all the information that can tell us what the atmosphere is doing."

While above average temperatures in the region are still expected this weekend, the 30 day forecast and long range forecast call for below to near normal temperatures for the rest of the month and throughout the spring.

When asked if the warm Arctic winter weather represents a symptom of global climate change, Bilan-Wallace said it fits the model.

"One day, one season, one year does not mean a trend. However, what's happening is not unexpected to people who are studying the issue of climate change.

It's more pieces in the puzzle that may support the work and theories that climate change scientists have been looking at."

In the long term, changing weather patterns will affect the North.

"If this trend continues, of course there will be consequences," Bilan-Wallace said. "Anytime you have extreme weather it's going to impact in ways that aren't normal. That's really all I can say at this stage."

Art Barnes, Superintendent of the South Slave region for the GNWT Department of Transportation, has not observed any unusual deterioration of the ice crossing at Fort Providence.

"Right now the warmer temperatures are not manifesting into any significant changes out there," he said.

"We've had some warm weather, and if we get some really nasty warm weather it's going to impact us. But right now we're still OK."

It takes five to seven days of continuous 15C to 20C temperatures to significantly affect the crossing. In the past four decades the road has closed on April 20, except for the last five years, when it closed on April 18.

"What I've seen is that, almost in spite of what the winter weather does, that crossing lives up to its past record," Barnes said. "We're ever watchful for changes to that crossing because it's so important to our transportation system and the resupply of the community and industry."

Snowmobile routes are similarly unaffected by the extraordinary temperatures, according to Bruce Hewlko of the South Slave Snowmobile Association.

"The trails are rough but the lakes are in good shape and overflow is not really a problem," he said.

Snowmobile trails usually begin to deteriorate in early April.