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What is a Pineapple Express?

Staff writers
September 28, 2012 — From Alberta Clippers to Lake Effect Snow. Natalie Thomas takes a look at some fall weather terms that Canadians may start to hear over the next couple of months.

Windchill is calculated using the current wind speed and temperature
Windchill is calculated using the current wind speed and temperature

Students are back at school and fall is officially here. That means Canadians can expect to see some weather patterns that are often forgotten over the summer months.

Dayna Vettese, a meteorologist at The Weather Network offers a crash course on some common fall weather terms.


Windchill is a derived number that we use, and we calculate it using the current wind speed and the current temperature. And it really tells us what it feels like in the winter. Every province in Canada and every territory is susceptible to windchill.

Lake Effect

Lake Effect is the term that we use when we refer to precipitation that occurs over the lakes. What you need is cold air moving over relatively warm waters. The difference between the air and the water temperatures has to be at least 13 degrees, and then we get precipitation formation. Normally we see this towards the end of fall and throughout the winter season. The main regions in Canada that are affected by this are southern Ontario and northern Ontario with the Great Lakes, as well as through Manitoba.

Alberta Clippers are notorious for dropping temperatures
Alberta Clippers are notorious for dropping temperatures

Common fall storms: 

Alberta Clipper 

An Alberta Clipper is a low pressure system that forms off the Rocky Mountains in Alberta, and it moves very quickly - that's why it's called a clipper - across the provinces. It can affect anyone from Alberta right to Newfoundland depending on the current storm tracks. Generally, Alberta Clippers don't drop very much snow, but they are notorious for dropping temperatures. 


The Nor'easter is a large low pressure system that affects the eastern seaboard of North America. Generally they occur in the fall and winter. It causes a prevailing wind direction from the north east, to affect the Atlantic provinces. And when these occur we get strong winds, and anything from rain to freezing rain to snow.

Pineapple Express 

The Pineapple Express is a non-meteorological term given to the moisture that originates near the Hawaiian Islands, hence the term pineapple, and travels along the jet stream towards the west coast of North America. Generally British Columbia is the most affected by these systems, in the form of rain or snow and strong winds.

Wondering what the fall season will be like in your area? Be sure to check the 2012 Fall Outlook

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