Question: I was preparing for a night flight to get night current. It was a cold but clear night with a full moon. In the middle of the taxi to the runway at the nontowered airport, the fog dropped like a blanket. It was a surprise, since the TAF didn’t indicate fog. I know fog forms when the temperature and dew point converge, but is there a way to tell if it is on the way besides monitoring the temperature?
Answer: You are correct, as indicated in the Pilot’s Handbook of Aeronautical Knowledge, Chapter 12, “when the temperature of the air is reduced to the dew point, the air is completely saturated and moisture begins to condense out of the air in the form of fog, dew, frost, clouds, rain, or snow.”
