FAA Part 107 Remote Pilot (UAG)WeatherHard
A TAF for the planned operating area includes the group: 'FM1800 22015G25KT P6SM BKN020'. What does the 'FM1800' portion of this forecast indicate?
- AThe forecast is valid for exactly one hour beginning at 1800Z
- BThere is an 18% probability of the stated conditions occurring after 2000Z
- CA temporary fluctuation in conditions is expected sometime between 1800Z and 2000Z
- DA rapid and significant change in conditions is forecast to begin at 1800Z and continue until the next change group
Show answer & explanationAnswer & explanation
Correct answer: D. A rapid and significant change in conditions is forecast to begin at 1800Z and continue until the next change group
'FM' stands for 'From' and marks a rapid, significant, and lasting change in prevailing conditions beginning at the specified time (1800Z in this case). The new conditions listed after FM completely replace the previous forecast group and remain in effect until the next FM, BECMG, or the end of the TAF period.
Why the other options are wrong
- A. FM groups are not limited to one hour; they remain valid until the next change group in the TAF.
- B. Probability groups use PROB30/PROB40, not FM, to indicate a percentage chance of conditions.
- C. Temporary fluctuations are indicated by TEMPO, not FM, and would show a time range rather than a single onset time.
TAF FM Group
In a Terminal Aerodrome Forecast, 'FM' followed by a time indicates a rapid, significant, and lasting change in conditions beginning at that time, replacing all prior forecast conditions.
- FM time is given in four digits UTC (e.g., FM1800 = 1800Z)
- Conditions after FM remain valid until the next FM or BECMG group
- Differs from TEMPO, which denotes temporary, short-lived fluctuations
Memory trick: 'FM = From this moment forward — like flipping a light switch instantly.'