The visible satellite image at left shows the tops of thunderstorms mushrooming along the trough extending southward from the low pressure system over Quebec described in the previous post below. These storms flipped a truck on the Champlain Bridge in the middle of rush hour in Montreal, leading to a 7 truck pile up. Amazingly, no one was killed. Winds also knocked out power at LSC and at my home in Frelighsburg, QC.

A long line of thunderstorms like this is called a squall line and accounts for most of the severe thunderstorms in our area.

The animated visible satellite image shows how quickly these thunderstorms grow in the hour between 18Z and 19Z. It seems that these storms form as the trough hits the Lake Champlain Valley. This rapid formation is why thunderstorms are so difficult to predict. The trough and cold front which triggered the storms could be seen days before, but if these storms erupted an hour later the Champlain Valley and Montreal would have been missed entirely!

High resolution visible satellite satellite imagery for Vermont can be accessed at the LSC Meteorology Department website.