Why is the GFA not always reflecting the weather described in the TAF?
An aerodrome forecast (TAF) is the most probable weather conditions, within 5 miles of a given site, at the most probable time of their occurrence. A graphic area forecast (GFA), on the other hand, depicts the range of conditions that are likely throughout a large geographic domain. To have a TAF that is different than the GFA is therefore not unusual. For example, the GFA may indicate that there are isolated thunderstorms over a defined area, but the aviation meteorologist may have good reasons to believe that they may not affect a given aerodrome, so the TAF makes no mention of it. The reverse situation, however, should not occur. For example, if a TAF says freezing precipitation and the GFA does not – that would bear some investigation.
