Why London is snowbound, and Toronto isn't

London is still buried in snow and much of the city has ground to a halt, but the mayor will not be declaring a state of emergency. “I’m not calling in the army,” said Mayor Joe Fontana.

But he will be shutting down the public transportation service as of 3 p.m. Tuesday evening. He’s asking employers to give their workers time off or the opportunity to work from home. And he is urging young people to knock on their neighbours’ doors, offer to shovel and go for groceries.

Fontana said more snow has fallen in the past two days than in any two days in the city’s history. The city has borrowed snow removal equipment and crews from neighbouring municipalities.

“Every time we seem to clear the main roads, we’re having to go back into them,” he said.

“Our people have been working day and night.”

So far there have been no power outages or serious injuries. And surrounding municipalities have been largely spared the onslaught.

“It seems to be stalled over London. I don’t know why we’re so lucky,” mused the mayor.

David Phillips, a senior climatologist at Environment Canada, said it’s the “lake effect.”

“You drive 15 minutes away and you can see green grass,” said Phillips.

“Talk about a world of difference.”

Why? It’s the lake effect snowstorm, snow burst or “streamer” effect.

What is it? At this time of year the Great Lakes are much warmer than the air above them, said Phillips.

The air sucks moisture out of the lake and then moves over the land, where it dumps out the moisture in the form of snow.

These “streamers” only form when there is a very steady wind pattern, he said. How does it work? In this case, the wind has been blowing in the same direction (west-northwest) for several days in a row.

The streamer drifting off Lake Huron is now “locked in” over London, said Phillips, and the snow continues to fall.

These bands of air are often very narrow, which explains why one city can be experiencing whiteout conditions, while the next town over has only a light dusting of snow.

Last year London had about 108 cm total.

Are we next? No, said Phillips, because Toronto isn’t usually downwind of Lake Ontario. Toronto can experience lake effect snow bursts, but only if the wind is moving in an easterly direction which isn’t common. But there is a traditional snowstorm heading north from the United States.

It’s too early to predict how much snow will get dumped on Toronto, but look for flurries beginning this Sunday.

-- Cynthia Vukets, Staff Reporter