What does the METAR code 'FG' stand for?

In METAR reporting, the code 'FG' is used to indicate the presence of fog. Fog is an atmospheric condition characterized by the suspension of water droplets in the air, which reduces visibility to less than 1,000 meters (approximately 3,280 feet). This reduction in visibility is essential for pilots and air traffic controllers, as it can greatly impact flight operations and safety.

Understanding this METAR code is crucial, as it directly affects the decision-making process in aviation. Pilots must be aware of fog conditions when planning departures, arrivals, and overall flight safety. Therefore, the presence of 'FG' in a METAR report serves as a critical alert regarding potentially hazardous weather conditions resulting from reduced visibility.

The other options, while related to weather phenomena, do not correspond to the 'FG' code in METAR reports. For instance, freezing rain is indicated by a different code, and 'freezing fog' has a separate designation. Thunderstorms, too, are reported using specific codes that do not include 'FG'. Thus, recognizing 'FG' as fog is vital for interpreting METAR data accurately.