How is fog that covers a substantial part of the station coded when the prevailing visibility is 7 miles?

When fog covers a substantial part of a weather observation station and the prevailing visibility is 7 miles, it is essential to accurately code this phenomenon to convey the appropriate information to pilots and meteorologists. The correct code for fog that obscures visibility but does not reduce it to below 7 miles is "PRFG," which stands for "partial fog."

The term "partial fog" indicates that while fog is present, it is not reducing visibility below the threshold considered to be problematic for flight operations. In this scenario, since the visibility remains at 7 miles, the presence of fog is significant enough to warrant the "PRFG" code.

Understanding how fog and visibility interact helps in recognizing the impact of various weather phenomena on aviation operations, especially during critical stages like take-off and landing. In contrast, other codes such as "BR" represent mist, "MIFG" refers specifically to shallow fog, and "BCFG" is used for patchy fog. These codes serve different conditions or intensities of fog and visibility, clarifying their specific contexts. Thus, the choice of "PRFG" effectively communicates the situation at the station.