How to read a TAF
Understand a terminal aerodrome forecast — its validity period, change groups (FM, TEMPO, BECMG) and how it differs from a METAR.
A TAF (terminal aerodrome forecast) is a forecast of conditions expected within about 5 statute miles of an airport, usually valid for 24 or 30 hours and issued four times a day. It uses the same coding as a METAR, plus change groups.
`KJFK 121130Z 1212/1318 18010KT 6SM -RA BKN015 FM121800 21015G25KT P6SM SCT040 TEMPO 1218/1222 4SM SHRA`
- 1212/1318 — valid from the 12th 1200Z to the 13th 1800Z.
- The first line is the prevailing forecast at the start.
- FM121800 — "from" 1800Z, a rapid, lasting change: wind 210°/15 gust 25, visibility better than 6 SM (`P6SM`), scattered 4,000 ft.
- TEMPO 1218/1222 — temporary fluctuations (lasting under an hour each, less than half the period) between 1800–2200Z: 4 SM in rain showers.
- BECMG — a gradual becoming change over a stated window.
- PROB30/40 — a 30–40% probability of the stated conditions (often for thunderstorms).
The key difference from a METAR: a METAR is what is, a TAF is what's expected. Read the validity period first, then walk the timeline to your estimated arrival, applying each FM/TEMPO/BECMG group in turn. Cross-check the TAF against the latest METAR — if reality is already diverging from the forecast, trust the trend.
*Reference and training only. Use official briefings for flight planning.*