TAF Abbreviations: The Forecast Codes, Decoded

Most TAF abbreviations are METAR abbreviations. Wind, visibility, weather and cloud all use the same codes in both, and a pilot who can read one can read four fifths of the other.

What makes a TAF different is a small set of codes that only make sense about the future. Those are the ones this page covers.

The TAF abbreviations a METAR never uses

These are the forecast-only codes. Everything else in a TAF body comes from the shared vocabulary.

For the wind, visibility, weather and cloud codes, which are identical in both products, see the full METAR abbreviations list.

The change groups build the timeline

Four codes turn a list of weather into a forecast with a timeline, and they behave very differently from each other.

FM starts a new steady state at a stated time and cancels everything before it. Everything after it is the prevailing forecast until the next change.

TEMPO marks short bursts inside a window. It does not replace the forecast around it. Each burst should last under an hour. Together they should cover under half the window.

BECMG describes a gradual change across a window. The change starts somewhere inside it and is finished by the end.

PROB30 and PROB40 give odds on conditions happening at all. There is no PROB50, because at that point the forecaster is expected to commit.

Reading the valid period

The period sits right after the issue time, and it uses a form a METAR never needs.

0512/0612 means from 1200 on the fifth to 1200 on the sixth. Four digits each side: two for the day, two for the hour. Minutes are never given.

Most TAFs run 24 or 30 hours. Larger airports get the longer version, because more traffic plans further ahead against them.

An amended TAF shortens the period rather than restarting it. An amendment issued at 1500 for a forecast ending at 0600 will run 1500 to 0600, not a fresh 24 hours from 1500.

The codes that mean more than they look

Three forecast codes carry more weight than their length suggests.

P6SM means greater than six statute miles. Forecasters rarely predict an exact visibility above six miles, so this stands in for anything better. Its opposite in a METAR is M, meaning less than.

WS marks low-level wind shear that no storm caused. It is the one to slow down for. WS010/27050KT says the wind at 1000 feet above the field is 270 at 50 knots. The surface wind is whatever the body says. The gap between the two is the hazard.

NSW means no significant weather, and it only appears inside a change group. It is how a forecast says the rain has stopped, rather than simply omitting the weather group.

What a TAF leaves out

Knowing what is missing is as useful as knowing what is there.

There are no remark groups. No sea-level pressure, no temperature to a tenth of a degree, no hourly precipitation, no peak wind. All of those record something measured, and a forecast measures nothing.

There is no altimeter setting in a civil TAF either. A military TAF adds one, as QNH2992INS, along with numeric icing and turbulence groups a civil forecast never carries.

And a TAF only covers about five statute miles around the field. It is an aerodrome forecast, not an area forecast, so weather twenty miles away is somebody else's product.

How a TAF is laid out

The order never varies, so you can find any part by counting.

First the type, then the station, then the issue time. Then the valid period. Then the first block of weather, which is the prevailing forecast at the start.

After that come the change groups, in time order. Each one carries its own weather, and each applies until the next one that replaces it.

Groups can be missing from any block. If no weather group appears, no reportable weather is forecast. Nothing shifts along to fill the gap, so a missing group is a fact rather than an error.

Read your arrival time first, then find the block that covers it. That block is your forecast. Anything layered on top of it modifies that answer.

Verdict on TAF abbreviations

Learn the change groups first, because they are the part that is genuinely new. FM replaces, BECMG slides, TEMPO interrupts, and PROB puts odds on it.

Everything else in the body is vocabulary you already have from METARs. Read the valid period, find the segment covering your arrival time, then apply whatever is layered on top of that segment.

Last updated August 29, 2026