Definition
The movement of a weather front (the boundary between two air masses of different temperature, humidity, or density) across an area, producing rapid changes in wind direction, wind speed, temperature, and pressure. Passing frontal systems are a recognized source of low-level wind shear, particularly during and shortly after frontal passage when winds in the lowest few thousand feet can shift abruptly.
Plain English
When a weather front moves across your location, the wind near the ground can change direction and speed quickly, which can be hazardous on takeoff, approach, and landing.
Context Anchor
Seen in weather briefings, forecasts, and low-level wind shear discussions for takeoff, approach, and landing.
Derivation
Frontal comes from the military term front, meaning the line where two opposing forces meet. Meteorologists borrowed it in the early 1900s to describe the boundary where two air masses meet and clash. A passing front is simply that boundary moving through your area.
Why Pilots Care
These moving fronts are a common trigger for low-level wind shear that can suddenly reduce airspeed or lift during critical phases of flight.
Grounding Statement
Picture a moving line of weather crossing the airport; before it arrives the wind may be one way, and after it passes the wind may be noticeably different.
Intuition Check
Do not read “passing” as “minor” or “already gone.” Here it means the front is moving through the area, and the wind can change while it is passing.
Example Sentence 1
The TAF showed a passing frontal system around the time of our arrival, so we briefed for possible wind shear on final.
Example Sentence 2
After the cold front passed the airport, winds shifted forty degrees and required a go-around.