Understanding TAF Forecasts for Flight Planning

While METARs tell you what the weather is, TAFs tell you what the weather will be. Terminal Aerodrome Forecasts are essential for any flight that extends beyond the next hour.

What Is a TAF?

A TAF is a weather forecast for a specific airport, covering a 24- or 30-hour period. They're issued four times a day and amended when conditions change unexpectedly.

Breaking Down a TAF

TAF KORD 101730Z 1018/1124 27015G25KT P6SM SCT040 BKN080
  FM102200 30012KT P6SM FEW050
  TEMPO 1100/1106 3SM -TSRA BKN030CB
  BECMG 1106/1108 24008KT P6SM SCT050

Header

TAF KORD 101730Z 1018/1124 — A TAF for O'Hare, issued on the 10th at 17:30Z, valid from the 10th at 18:00Z to the 11th at 24:00Z (midnight).

Initial Conditions

27015G25KT P6SM SCT040 BKN080 — Wind 270° at 15 gusting 25 knots, visibility greater than 6 statute miles, scattered clouds at 4,000 and broken at 8,000 feet.

Change Groups

FM (From) — A permanent change starting at a specific time. FM102200 means from the 10th at 22:00Z, conditions shift to 300° at 12 knots, visibility over 6 miles, few clouds at 5,000.

TEMPO — Temporary fluctuations expected for less than half the time period. TEMPO 1100/1106 means between the 11th 00:00Z and 06:00Z, expect occasional 3SM visibility in light thunderstorms with rain.

BECMG — A gradual change. BECMG 1106/1108 means between 06:00Z and 08:00Z the weather will transition to the new conditions.

Other Change Indicators

  • PROB30/PROB40 — 30% or 40% probability of the described conditions
  • AMD — Amended forecast (replaces previous TAF)
  • COR — Corrected forecast

How to Use TAFs for Flight Planning

  1. Check departure and destination TAFs — Ensure conditions are above your personal minimums at both ends.
  2. Look at the full forecast period — Don't just check arrival time; consider what happens if you're delayed.
  3. Pay attention to TEMPO groups — Temporary conditions could make your approach challenging.
  4. Have alternates ready — If the TAF shows PROB40 or TEMPO for low conditions at your destination, pick a solid alternate.

TAF vs. METAR

Use them together: the METAR confirms what's happening right now, and the TAF shows the trend. If the METAR is already worse than the TAF predicted, be extra cautious — the forecast may be behind reality.