Motorists cautioned as dense fog blankets parts of southern Ontario

Motorists across southwestern Ontario are being warned to take caution this morning, after a bank of dense fog rolled in over the area overnight.

Wednesday night's cool weather and clear skies made it a great evening for a walk and a little stargazing. However, that cool, clear night also set up perfect conditions for this morning's pea-soup fog as the winds brought in a batch of warm, humid air just before sunrise. The cool ground sapped the heat from this moisture-laden air, and as the air cooled, all the water it was holding condensed out to form 'advection fog' — essentially a ground-level cloud.

Environment Canada issued a special weather statement for regions from Waterloo-Wellington, through the Hamilton and Niagara areas and into the western end of the GTA. Motorists are advised to be cautious, as visibility on the roads could drop to zero at times. Valleys and lower-lying areas will likely have the heaviest fog, so take particular care when driving through those areas on your commute.

[ More Geekquinox: Green-glowing Comet ISON should survive its trip around the sun ]

The fog won't last too long, fortunately. As the sun gets higher in the sky later this morning, and the ground and air warm up, the ground-level cloud will evaporate again and return us to clear driving and clear skies.

(Image courtesy: Ontario Ministry of Transportation)

Geek out with the latest in science and weather.
Follow @ygeekquinox on Twitter!