What does the broken cloud layer written as BKN250 indicate on a TAF?

When a TAF (Terminal Aerodrome Forecast) states BKN250, it indicates a broken cloud layer at 25,000 feet above mean sea level (MSL). In aviation, cloud heights are typically referenced to MSL, which is the standard for meteorological reports and forecasts.

The term "broken" signifies that between 5/8 and 7/8 of the sky is covered by clouds at that specified altitude. Therefore, the specification of 250 in BKN250 means that pilots can expect significant cloud coverage starting at this high altitude. Understanding cloud layers is crucial for flight planning and safety, as it can affect visibility and the overall flying conditions.

The distinction between feet AGL (Above Ground Level) and MSL is critical in interpreting aviation weather reports, with MSL being the more commonly used standard for altitude in sky classifications.