How does FG differ from BR in a METAR?

Fog (FG) and mist (BR) are both meteorological phenomena that affect visibility, but they have different characteristics that are reflected in METAR reports. In the context of visibility reported in METARs, FG represents a more severe reduction in visibility than BR.

When FG is reported, it signifies that visibility is reduced significantly, typically to less than 1 kilometer (or less than 1/2 mile), that can be attributed to the presence of tiny water droplets suspended in the air. This condensation occurs when the temperature and dew point are very close together, leading to dense visibility conditions. Consequently, FG indicates that pilots and crew must be cautious due to significantly lowered visibility that affects navigation and operational safety.

On the other hand, BR indicates mist, which results in a lesser degree of visibility reduction compared to fog. In cases of mist, visibility may still be relatively good but is somewhat compromised, often reported between 1 and 5 kilometers (approximately 1/2 to 3 miles).

Thus, the distinction made between FG and BR in METARs is crucial for flight operations, as FG signifies a more critical visibility loss, necessitating more caution in navigation and approach procedures. This understanding of visibility categories is essential for pilots, dispatch