A TAF is a forecast for the area within about 5 statute miles of an airport, usually covering 24 to 30 hours. A METAR tells you what the station is reporting now. A TAF tells you how the forecast changes across a valid period. Section 107.49 still requires you to assess local weather before flight. The TAF is how you see the afternoon, not just the launch minute. The codes inside the forecast match METAR codes, which is why the test asks you to identify the product before you decode a group.
The header and the valid period
A course example:
TAF KXYZ 121130Z 1212/1312 25010KT P6SM SCT030
FM121800 28015G22KT P6SM BKN025
TEMPO 1220/1223 3SM -SHRA
PROB30 1300/1304 2SM TSRA
The first time, 121130Z, is when the forecast was issued: the 12th at 1130Z. The next group, 1212/1312, is the valid period. It is day and hour, Zulu, written DDHH/DDHH. 1212/1312 runs from the 12th at 1200Z to the 13th at 1200Z. 1218/1318 runs from the 12th at 1800Z to the 13th at 1800Z. It is not 12:18 to 13:18 local, and it is not "12 hours starting at noon" unless the hours actually say that. Read the four digits as day, then hour. In the sample, TEMPO 1220/1223 is the 12th from 2000Z until 2300Z, and PROB30 1300/1304 is the 13th from 0000Z until 0400Z.
P6SM means visibility greater than 6 statute miles. Wind, sky, and weather groups mean the same thing they mean in a METAR. Wind direction is still degrees true.
FM, TEMPO, and PROB30
Standard National Weather Service TAFs use three change groups you should be able to name.
FM means FROM. Prevailing conditions are expected to change significantly in less than an hour. The new group replaces the previous prevailing forecast from that time until the next FM or the end of the TAF. FM121800 means the new prevailing conditions begin at 1800Z on the 12th.
TEMPO means temporary fluctuations. Each instance is expected to last less than one hour, and the fluctuations cover less than half of the indicated period in total. The TEMPO window should be only as long as needed and should not exceed four hours. TEMPO does not become the new prevailing forecast. A change-group time uses the same DDHH/DDHH form as the valid period. TEMPO 1920/1922 runs from the 19th at 2000Z until the 19th at 2200Z. It does not mean 19:20 to 19:22. If the flight is on the 19th from 2000Z to 2100Z and the TAF says TEMPO 1920/1922 3SM SHRA, brief showers and 3 statute miles are possible during the flight. The prevailing group may still show better weather. Plan for the temporary group. Do not ignore it because it is not the base line.
PROB30 means a 30 percent chance of thunderstorms or precipitation, and the weather directly tied to that event, during the stated hours. In a standard NWS TAF, PROB30 is the probability group in use. NWS does not use PROB40. The older practice of keeping PROB30 out of the first nine hours was removed in NWSI 10-813 on October 30, 2024. U.S. military and international TAFs can look different. BECMG, a gradual change, appears in some of those formats. NWS does not use BECMG in a standard U.S. TAF. If a Part 107 item is about a U.S. civil TAF, do not pick BECMG as the NWS temporary group.
Using it on a job
Translate the forecast into the Part 107 minimums before you promise a launch time. Visibility at the control station must be at least 3 statute miles. The aircraft must stay 500 feet below clouds and 2,000 feet horizontally from them, and at or below 400 feet AGL unless the structure exception applies. A TEMPO group of 3SM is the edge of the visibility rule, not a comfortable margin. A PROB30 thunderstorm group is a reason to move the job. Thunderstorms bring turbulence, hail, lightning, and outflow that a small multirotor does not shrug off.
The TAF covers the airport area, about 5 statute miles. A site well away from the airport can differ. §107.49's weather assessment is local. Use the TAF, then look at the sky you are actually under.
Pair every TAF with a current METAR, on the METAR page, and with NOTAMs. Weather and airspace restrictions are separate preflight items. A clear TAF does not cancel a TFR.