Understanding TAF Forecasts
How to read Terminal Aerodrome Forecasts and use them for flight planning.
What is a TAF?
A TAF (Terminal Aerodrome Forecast) is a weather forecast for the area within 5 statute miles of an airport, typically covering a 24 to 30-hour period. TAFs are issued four times daily (every 6 hours) and use a format similar to METARs.
TAFs are the primary tool for understanding expected weather conditions at your destination and alternate airports. Unlike METARs (which report current conditions), TAFs tell you what to expect during your flight and arrival.
Example TAF
TAF for San Francisco International Airport (KSFO)
Reading the TAF Header
Report type (TAF) and ICAO station identifier
Issuance date/time: day 04, time 17:30 UTC
Valid period: day 04 from 18:00Z to day 05 at 24:00Z (30-hour TAF)
TAF Change Groups
A permanent change in conditions starting at the specified time. All previous conditions are replaced.
A gradual, permanent change expected to occur within the specified time window.
Temporary fluctuations lasting less than 60 minutes at a time and occurring less than half the period.
30% or 40% probability of the specified conditions occurring during the time period.
Using TAFs for Flight Planning
- 1
Check the TAF for your departure airport — look for any deteriorating conditions near your planned departure time.
- 2
Review the destination TAF for your ETA window — check for TEMPO or PROB groups that could affect landing.
- 3
Identify the ceiling and visibility at your alternate airport throughout your flight.
- 4
Note any SIGMET or AIRMET activity that may affect your route.
- 5
Compare the TAF forecast with the latest METAR to see if conditions are trending as forecast.
Frequently Asked Questions
How long does a TAF cover?
Standard TAFs cover a 24-hour period and are issued four times daily (every 6 hours). Extended TAFs cover 30 hours and are issued at major airports. TAFs are valid for the area within 5 statute miles of the airport.
What is the difference between TEMPO and BECMG in a TAF?
TEMPO (temporary) indicates conditions expected to last less than 60 minutes at a time and for less than half the forecast period. BECMG (becoming) indicates a gradual, permanent change in conditions expected to occur within a specified time window.
What does PROB30 or PROB40 mean in a TAF?
PROB30 means there is a 30% probability of the specified conditions occurring. PROB40 means 40% probability. These are used for conditions that are possible but not expected to be the dominant scenario. PROB values below 30% are not used in TAFs.