What is orographic lifting?
Atlantic Canada's proximity to the ocean and vast differences in terrain means that our weather can vary significantly over small distances.
Take last week, for example, when 50-plus cm of snow fell in parts of Victoria County, Cape Breton, with much less on the other side of the Highlands, and the onshore snow in western Newfoundland earlier this week.
The two events have something in common — mountains.
The Appalachian Mountain range extends from western Newfoundland into the Cape Breton Highlands, with sections of the range on parts of mainland Nova Scotia and northern New Brunswick.
Precipitation happens because of upward vertical motion, which is caused by various factors, including mountains, through a process known as orographic lift or upsloping.
When the wind blows horizontally at the surface but encounters a mountain range, the air is forced to rise. The rising air can cool to a point where it reaches the condensation level, leading to rain or snow.
The amount of moisture and duration of these winds can lead to significant amounts of precipitation.
This effect is often found along the Rocky Mountains and on the state-side section of the Appalachians due to their higher ranges but does occur here sometimes, especially if winds blow perpendicular to the mountains.
That's why the Cape Breton Highlands and Long Range mountains often receive much more precipitation than anywhere else in our region.
Orographic lifting can also lead to warm, dry conditions on the leeward side of the mountain.
Think of Alberta's chinooks as a prime example.
Our mountains aren't tall enough for the exact same effect. Still, lower precipitation and, at times, warmer conditions can occur here, too, under certain circumstances.
It's a great example of how mountains can tremendously impact our weather.