Air moves from high pressure to low pressure. The bigger the difference over a short distance, the harder it moves. That difference is called the pressure gradient, and it’s the engine behind our strongest winds.
In southern Alberta, a classic setup is high pressure over B.C. and a low or trough sitting over the prairies east of the mountains. Air rushes down the slopes and across the plains, and Lethbridge sits right in its path.
Clues you can watch yourself
- Pressure dropping steadily over several hours. A fall of 3 hPa or more in three hours often means wind is coming.
- A chinook arch: the long, straight band of cloud over the mountains with clear sky underneath. It means strong west winds aloft.
- A rapid pressure rise after a storm, which often brings strong north or northwest winds as the cold air arrives.
What to do
- When the pressure is falling fast, tie things down early rather than waiting until the gusts arrive.
- If you’re planning to tow, haul a trailer or drive a high-sided vehicle, check the trend before you leave.
The station at westlethbridgeweather.com shows barometric pressure and whether it’s rising or falling. It’s one of the best early clues you have.
Related: Live conditions at West Lethbridge Weather · Wind in Lethbridge
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