Under what condition should sector visibility be reported in the remarks?

Sector visibility should be reported in the remarks when it differs from the prevailing visibility by one or more reportable values and is less than 3 miles. This is crucial for providing accurate and specific weather information that can impact aviation operations and surface observations. Reporting sector visibility in these circumstances helps in identifying localized conditions that may differ significantly from the general visibility, which is essential for flight safety and situational awareness.

When sector visibility is less than 3 miles, it indicates potential issues such as fog, precipitation, or other obstructions that could affect visibility in specific directions. By noting this in the remarks, weather observers ensure that pilots and meteorologists receive comprehensive and actionable information about potentially hazardous conditions in specific sectors of the atmosphere.

In contrast, if sector visibility exceeds a certain threshold or aligns with prevailing visibility, the need for reporting as a remark becomes less critical since it does not provide additional relevant information that would impact decisions. Notably, this ensures that critical information is conveyed without cluttering reports with less significant data.