SkyDrill

Meaning of the FM change group in a TAF

Remote Pilot (Part 107) practice question 14 of 18 on Weather / Sources. ACS element UA.III.A.K2 · difficulty: standard. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONA TAF contains the change group FM1500. What does the FM indicator tell the remote pilot?

  1. AA rapid and significant change expected at 1500Z
  2. BTemporary fluctuations lasting less than 1 hour, starting at 1500Z
  3. CA 30 percent probability of thunderstorms after 1500Z
Show the answer and explanation

Correct answer: A. A rapid and significant change expected at 1500Z

  • A — correct The study guide states FM is used when a rapid and significant change, usually within an hour, is expected, and the following digits give the time the new conditions begin.
  • B — incorrect Temporary fluctuations expected to last less than one hour are coded with TEMPO, not FM.
  • C — incorrect Probability of thunderstorms and precipitation is coded with PROB30, not with an FM group.

BACKGROUND

The forecast change group in a TAF describes any significant weather change forecast to occur during the TAF period, along with the expected conditions and time. The change may be shown as FM (from) or TEMPO (temporary). FM is used when a rapid and significant change, usually within an hour, is expected. TEMPO is used for temporary fluctuations of weather expected to last less than one hour. A separate PROB30 group gives the probability of thunderstorms and precipitation in the coming hours and is not used for the first six hours of the 24-hour forecast.

STUDY TIP

Sort the three indicators by what they describe: FM is a lasting change from a given time, TEMPO is a brief fluctuation, and PROB30 is a probability statement.

KEY POINTS

  • FM marks a rapid, significant change, usually within an hour, beginning at the stated time.
  • TEMPO marks temporary fluctuations expected to last less than one hour.
  • PROB30 gives a probability of thunderstorms or precipitation.

SOURCES

  • remote_pilot_study_guide.txt, Chapter 3a "Terminal Aerodrome Forecasts (TAF)", items 9 Forecast change group and 10 PROB30
Practice the Remote Pilot (Part 107) test →Timed 60-question exam, by ACS area, or review your misses. Free.
MORE ON WEATHER / SOURCES

SkyDrill is not affiliated with the FAA. This is an original practice item based on 14 CFR part 107, 14 CFR part 89, and the FAA Remote Pilot – Small UAS Study Guide (FAA-G-8082-22). Regulations and handbooks are revised; confirm details against the current edition.