Iqaluit (Feb 23/04) - It may glitter like tiny diamonds in the air and create soft, delicate looking clouds, but this stuff grounds airplanes for hours and is almost impossible to forecast.

It's got a new official name now: freezing fog.

Ice fog is the layman's term for the phenomenon that creates clouds on roadways and at airports in regions where the temperature dips from -20 to -40 and below.

"Ice fog goes right from a gas to solid ice crystals," explained Yvonne Bilan-Wallace, a meteorologist with Environment Canada, who still uses the term ice fog when explaining how it works.

"In very clean air you won't get ice fog until -40.

If there is dirt in the atmosphere, ice fog can appear at -20."

Ice fog is notoriously difficult to forecast, Bilan-Wallace added.

Everything affects how much glittering fog is actually in the air.

Chimney stacks, car and airplane exhaust, even the breath of dogs and herds of animals -- many things conspire to mess up the weather forecast and create freezing fog.

"We have the joke when our forecast goes bust, we go, 'oh, it must have been a caribou herd coming too close to the airport!'" Bilan-Wallace said.

Forecasters have to use creative methods to inform the public where freezing fog is, and how long it will hang in the air.

The forecaster will look at access to open water, wind direction and the topography of the area to determine how bad the visibility is going to be.

"It can become a real problem," Bilan-Wallace said.

"It will sometimes form a coating on pavement, making black ice.

"You know how it forms on your car. Well, just imagine that on a roadway."

Gjoa Haven's expert says...

Troy Beaulieu, observer/communicator with the Community Aerodrome Radio Station in Gjoa Haven, produces hourly weather reports in the region.

He said this year, freezing fog has not been a problem.

"It's been so cold," Beaulieu said.

"Mostly we get ice crystals. Last year was bad (for freezing fog) because of warmer temperatures."

Ice crystals are different than freezing fog.

Freezing fog forms a coating on things, while ice crystals just hang in the air and look pretty when light shines through them.

On gravel roads, freezing fog isn't so bad.

But it can make hard packed snow very slippery.

Beaulieu, who worked as a weather observer in the NWT for 10 years before moving to Gjoa Haven, said the worst freezing fog he has ever seen was in Gjoa Haven.

"It's because we're so close to the ocean. The ocean wraps three-quarters around us."

And where you've got moisture meeting cold, cold air, you've got freezing fog.