Glossary

The red line with semi-circles shows a warm front moving into BC from the Pacific Ocean.

A bird’s eye view of a low pressure system and its associated fronts. Coloured arrows indicate wind direction and air temperature.

A vertical slice through a warm front showing the gradual ascent of warm, moist air over the cold air it is advancing upon.

A warm front is the interface that occurs when a warm air mass replaces a retreating cold air mass. Warm fronts generate atmospheric lift as their associated low-density air mass climbs up and over the cooler, denser air it advances upon. This gradual overrunning of warm, moist air produces clouds and precipitation well ahead of the warm front’s surface position. Warm fronts are represented on weather maps by a solid red line with red semicircles pointing in the direction the front is moving.

Warm Front