Fred is a certified weather observer, but the station is officially
closed.

Then Fred is not certified to take weather observations at that station.

If your FBO has a
certified weather observer on staff it's because he's at a certified weather
observing station.

Ok, I should have read on a bit more before posting. I take it that a
certified weather observer loses his certification every time the
station closes (say for the evening), and regains it whenever the
station opens in the morning. So if Fred goes there when the station is
closed, and does =exactly= the same thing he would have when it was open
(except for the reporting path), then the observation is not official.

Is this ultimately what it rests on?

Jose