A Terminal Aerodrome Forecast (TAF) is a coded weather forecast issued for a specific airport, covering expected conditions over the next 24 to 30 hours. It includes wind, visibility, weather phenomena, and cloud layers in a standardized international format.
How It Works#
Meteorologists at approved forecast offices produce TAFs on a regular schedule. Major airports receive updates every six hours, issued at 0000, 0600, 1200, and 1800 UTC. Smaller airports may receive 24-hour TAFs instead of the full 30-hour version.
Each TAF follows a fixed structure defined by ICAO. The forecast opens with the airport's four-letter ICAO identifier, the issue time, and the valid period. After that, it lists the expected wind direction and speed, prevailing visibility, present weather, and cloud layers in sequence.
TAFs use change groups to signal shifts in conditions within the forecast period. The three main change groups are:
- FM (From): A complete, rapid change starting at a specific time.
- TEMPO (Temporary): Fluctuating conditions lasting less than one hour at a time, occurring for less than half the forecast period.
- BECMG (Becoming): A gradual, permanent change occurring within a defined time window.
Visibility and cloud height in a TAF use the same encoding as a METAR (Meteorological Aerodrome Report), so pilots familiar with one format can read the other without extra training.
Example in Aviation#
A pilot planning a morning departure checks the TAF for her destination airport. The forecast reads BKN015 for her arrival time, meaning a broken ceiling at 1,500 feet. A TEMPO group later in the forecast shows FM conditions dropping to OVC005 and half a mile in fog.
That combination falls below her personal minimums for an instrument approach. She delays the flight two hours until the TAF shows improving conditions, turning a potential go/no-go call into a clear decision supported by data.
Why It Matters#
TAFs are a primary planning tool for any flight involving instrument approaches or extended cross-country routing. Regulations under 14 CFR §91.103 require pilots to review all available weather reports and forecasts before any flight under instrument flight rules (IFR). A TAF provides the forecast half of that picture.
Even visual flight rules (VFR) pilots benefit from TAFs. A forecast showing deteriorating conditions at your destination two hours after your planned arrival gives you time to choose an alternate, adjust your route, or simply stay on the ground.
Key Takeaways#
- TAFs cover a single airport for 24 to 30 hours, updated every six hours.
- The format is standardized by ICAO and used worldwide.
- Change groups (FM, TEMPO, BECMG) indicate how and when conditions shift.
- TAF encoding mirrors METAR format, making both easier to read together.
- Reviewing the TAF for your destination is a legal requirement for IFR flight planning.