Definition
A cold front advancing at roughly 30 knots or more, in which the cold air pushes under the warmer air ahead of it so steeply that the warm air is forced rapidly upward, producing a narrow but intense band of weather along and just ahead of the front. Typical conditions include towering cumulus or cumulonimbus clouds, heavy showers, thunderstorms, gusty winds, hail, and sometimes squall lines, followed by rapid clearing and a sharp drop in temperature behind the front.
Plain English
A cold front that is moving quickly, shoving warm air violently upward and creating a short, sharp burst of severe weather — strong storms, gusty winds, and heavy rain — that passes through fast and is followed by clearing skies and cooler air.
Context Anchor
Seen in aviation weather study, preflight weather briefings, surface analysis charts, and forecasts when a pilot is deciding whether weather along a route is safe to fly through or around.
Derivation
In weather, “front” was borrowed from the idea of a battle front: a line where two opposing forces meet. Here, the opposing forces are different air masses. “Cold” tells you the advancing air is colder, and “fast-moving” tells you the boundary is traveling quickly across the ground.
Why Pilots Care
These fronts can generate wind shear, severe turbulence, and rapidly changing ceilings that force last-minute route or altitude changes.
Grounding Statement
Picture colder, heavier air sliding quickly under warm air and shoving it upward; that upward push is what can build rough weather near the front.
Intuition Check
Do not read “fast-moving” as just “the weather feels quick.” It means the front itself is moving quickly across the ground. Do not read “cold front” as only “colder temperature.” It is a moving boundary between air masses, and the weather near that boundary is what matters to pilots.
Example Sentence 1
The briefer warned of a fast-moving cold front crossing the route by mid-afternoon, with a squall line and embedded thunderstorms expected along the leading edge.
Example Sentence 2
With a fast-moving cold front approaching, the flight instructor advised delaying departure until the frontal passage and associated gusts had passed.