Definition
A type of air mass that forms over large, cold land areas in high latitudes, producing air that is cold and dry. In North America, cP air originates over the interior of Canada and Alaska and moves south to influence weather across much of the continent, especially in winter.
Plain English
Cold, dry air that builds up over cold land far to the north and then drifts south. When it arrives, it brings clear skies, low humidity, and sharply colder temperatures.
Context Anchor
Seen on weather charts and in FAA discussions of North American air mass source regions.
Derivation
The two-letter code follows a standard air mass labeling system: a lowercase letter for the surface it formed over (c = continental, meaning land) and an uppercase letter for the latitude/temperature of the source region (P = polar). So cP literally reads as 'land-formed, polar-origin' air.
Why Pilots Care
Helps predict stable weather, good visibility, and cold temperatures that influence flight planning and performance.
Grounding Statement
Picture cold, dry air sitting over frozen Canadian ground for days, soaking up the cold, then sliding south as a sharp, clear, frigid airmass.
Intuition Check
Polar does not mean the air must come from the North Pole itself. Here, it means the air formed in a cold, high-latitude region; continental means it formed over land, so it is usually dry.
Example Sentence 1
A cP air mass moved south overnight, bringing clear skies, gusty northerly winds, and temperatures twenty degrees below the seasonal average.
Example Sentence 2
Pilots checked the surface analysis chart to see how the cP air mass would affect visibility and density altitude at the destination airport.