Ground School
If you have already learned to read a METAR, the TAF is the natural next step. A METAR tells you what the weather is doing right now. A TAF tells you what it is expected to do over the hours ahead. For a pilot planning a flight, the forecast is often more important than the current conditions, because the question is rarely just what the weather is. It is what the weather will be when you arrive.
TAF stands for Terminal Aerodrome Forecast. Like the METAR, it is written in a compact code that looks intimidating at first and becomes second nature with a little practice. This guide breaks the TAF down piece by piece, using the international format that applies around the world.
A TAF is a coded weather forecast for the area immediately around an airport, typically within about five miles of the airport reference point. It is prepared by meteorologists and issued on a routine schedule, most commonly four times a day. Depending on the airport and the issuing authority, a single TAF covers either a 24-hour or a 30-hour period.
The TAF only forecasts the elements that matter to aviation: wind, visibility, significant weather, and cloud. It does not include the temperature forecasts that a public weather report would. Everything in a TAF is there because it affects whether and how an aircraft can operate.
A METAR is an observation. It reports the weather that is actually happening at a moment in time. A TAF is a forecast. It predicts the weather across a future window. They use almost the same codes for wind, visibility, weather, and cloud, which is why learning to read a METAR first makes the TAF much easier.
Every TAF begins with a header that identifies what it is, where it is for, when it was issued, and the period it covers. After the header comes the main forecast, followed by any change groups that describe how the weather is expected to evolve. Let us look at a complete example and decode it line by line.
TAF KORD 151730Z 1518/1624 21012KT P6SM BKN035
FM152000 24015G25KT P6SM SCT040
TEMPO 1521/1601 4SM -SHRA BKN025
FM160300 27008KT P6SM FEW250
PROB30 1606/1610 1SM BR
The SkyPrep course covers METARs, TAFs, and the weather theory behind them in a clear sequence.
The real skill in reading a TAF is understanding the change groups. These tell you when and how the weather is expected to shift during the validity period. There are four you need to know.
FM marks a rapid and lasting change at a specific time. Everything after it replaces the previous conditions completely. In the example, FM152000 means that from 2000 UTC on the 15th, the wind becomes 240 degrees at 15 gusting 25 knots, visibility stays above 6 miles, and the cloud becomes scattered at 4,000 feet. A FM group is a clean handover from one forecast state to the next.
TEMPO describes temporary fluctuations that are expected to last less than an hour each time they occur, and to cover less than half of the stated period. In the example, TEMPO 1521/1601 means that between 2100 UTC on the 15th and 0100 UTC on the 16th, the visibility may temporarily drop to 4 miles in light rain showers with broken cloud at 2,500 feet. These conditions come and go rather than settling in.
BECMG describes a gradual, permanent change that takes place over a stated period, usually a couple of hours. It does not appear in our example, but you will see it often. A group like BECMG 1602/1604 means the change happens progressively between 0200 and 0400 UTC on the 16th, and the new conditions then continue for the rest of the forecast.
PROB states the probability of a set of conditions occurring, expressed as a percentage, almost always PROB30 or PROB40. In the example, PROB30 1606/1610 means there is a 30 percent chance, between 0600 and 1000 UTC on the 16th, of visibility dropping to 1 mile in mist. A probability lower than 30 percent is not considered significant enough to forecast, and a near-certainty would simply be stated as expected rather than as a probability.
The TAF format is an international standard, but a few details vary by region. In the United States, visibility is given in statute miles, as in the example. In most of the rest of the world, visibility is given in meters, where a value such as 9999 means 10 kilometers or more. Some countries report wind in meters per second rather than knots. The structure and the change groups, however, are the same everywhere, which is what makes the format so powerful once you learn it.
Reading a TAF is not an academic exercise. Every cross-country flight begins with a weather briefing, and the TAF is at the center of it. A pilot who can read a TAF fluently can look at a forecast and immediately understand whether a flight is realistic, when the best window might be, and what alternate plans make sense. A pilot who cannot is dependent on someone else's interpretation.
This is exactly the kind of knowledge that is far cheaper and calmer to build on the ground than in the middle of training. Students who arrive already able to decode weather reports move through the weather portion of their training with far less stress.
METARs, TAFs, weather theory, and the decisions that flow from them are a core part of every pilot's knowledge. The SkyPrep course teaches all of it in a structured, plain-language sequence built for people starting from zero. Lifetime access means the material is there whenever you need to refresh it, through your licence and beyond.
Start Ground School for $79 Read Lesson 1 free firstA TAF, or Terminal Aerodrome Forecast, is a coded forecast of wind, visibility, weather, and cloud for the area around an airport, valid for 24 or 30 hours and issued several times a day. It shares almost all of its codes with the METAR, so learning the METAR first makes the TAF straightforward. The key to reading a TAF is the change groups: FM for rapid lasting changes, BECMG for gradual changes, TEMPO for temporary fluctuations, and PROB for the probability of significant conditions. All times are in UTC. Learn to read it fluently, and every flight you plan starts on solid ground.