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Morning fog hovers over parts of ON, QC

April 7, 2011 — Fog led to near zero visibility for some drivers in Ontario and Quebec Thursday morning.

Fog is simply a cloud near the surface of the earth
Fog is simply a cloud near the surface of the earth

It was a foggy start to the day for people living in Ontario and Quebec, especially along the shore lines of Lake Ontario or Lake Erie.

A moist air mass made for poor visibility on roads Thursday morning. At times, visibility dropped down to zero. In Lambton County, several school buses were cancelled because of the conditions.

The fog has since dissipated in most communities leading into a clear and sunny Thursday afternoon.

There is a possiblity of foggy patches persisting throughout the morning hours in southern Ontario on Friday.

“There is a small likelihood of fog appearing close to the lakeshore,” says Brian Dillon, a meteorologist at The Weather Network.

But, expect sunny and clear conditions on Friday and into the weekend. Temperatures are expected to reach a high of 15°C.

WHAT CAUSES FOG?

“Fog is formed when the air cools to a point that water vapour begins to condense,” The Weather Network's Chris St. Clair explains.“This moisture clings to particles in the air to form liquid cloud droplets, which are suspended.”

Advection fog forms when moist warm air flows over cold ground or water.

Radiation fog occurs when the warm, saturated ground begins to release its moisture to the air. With the absence of the clouds, the air is cooler. There's nothing to insulate or hold in the heat. Therefore, there's no lift patterns and the moisture begin to cool and fog is formed.

Fog is not unusual at this time of year. Meteorologists say it's often the result of the classic “spring vs. winter” battle.

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