TAF Decoder

Every forecast period in plain English, with the wind, visibility, weather, clouds and flight category you would plan on.

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TAF KJFK

Issued the 26 at 02:39 UTC · valid 26 03:00 to 27 06:00 UTC

TAF KJFK 260239Z 2603/2706 03026G38KT P6SM -RA SCT035 OVC080 FM260600 02027G38KT P6SM -RA SCT025 OVC035 WS020/02050KT FM261400 02028G39KT 6SM -RA OVC025 WS020/02050KT FM262000 01025G40KT 4SM RA OVC015 WS020/02050KT

Header
Group	Meaning
`TAF`	Report type Terminal aerodrome forecast
`KJFK`	Station Station KJFK (ICAO identifier)
`260239Z`	Issued Issued on the 26th at 02:39 UTC
`2603/2706`	Valid Valid from 26th 03:00 UTC to 27th 06:00 UTC

Prevailing forecast, 26th 03:00 UTC to 27th 06:00 UTC

VFR

03026G38KT P6SM -RA SCT035 OVC080

Wind: 030° 26 kt G38
Visibility: More than 6 SM
Weather: Light rain
Sky: SCT 3,500, OVC 8,000

Group by group

Groups in this period
Group	Meaning
`03026G38KT`	Wind Wind from 030° at 26 knots, gusting to 38 knots
`P6SM`	Visibility Visibility more than 6 statute miles
`-RA`	Weather Light rain
`SCT035`	Cloud layer Scattered clouds at 3,500 ft above the ground
`OVC080`	Cloud layer Overcast at 8,000 ft above the ground — a ceiling

From 26th 06:00 UTC: conditions change completely

VFR

FM260600 02027G38KT P6SM -RA SCT025 OVC035 WS020/02050KT

Wind: 020° 27 kt G38
Visibility: More than 6 SM
Weather: Light rain
Sky: SCT 2,500, OVC 3,500
Wind shear: 2,000 ft: 020° at 50 kt

Group by group

Groups in this period
Group	Meaning
`FM260600`	From From 26th 06:00 UTC, a new set of conditions replaces all earlier ones
`02027G38KT`	Wind Wind from 020° at 27 knots, gusting to 38 knots
`P6SM`	Visibility Visibility more than 6 statute miles
`-RA`	Weather Light rain
`SCT025`	Cloud layer Scattered clouds at 2,500 ft above the ground
`OVC035`	Cloud layer Overcast at 3,500 ft above the ground — a ceiling
`WS020/02050KT`	Low-level wind shear Wind shear: at 2,000 ft above the ground the wind is from 020° at 50 knots

From 26th 14:00 UTC: conditions change completely

MVFR

FM261400 02028G39KT 6SM -RA OVC025 WS020/02050KT

Wind: 020° 28 kt G39
Visibility: 6 SM
Weather: Light rain
Sky: OVC 2,500
Wind shear: 2,000 ft: 020° at 50 kt

Group by group

Groups in this period
Group	Meaning
`FM261400`	From From 26th 14:00 UTC, a new set of conditions replaces all earlier ones
`02028G39KT`	Wind Wind from 020° at 28 knots, gusting to 39 knots
`6SM`	Visibility Visibility 6 statute miles
`-RA`	Weather Light rain
`OVC025`	Cloud layer Overcast at 2,500 ft above the ground — a ceiling
`WS020/02050KT`	Low-level wind shear Wind shear: at 2,000 ft above the ground the wind is from 020° at 50 knots

From 26th 20:00 UTC: conditions change completely

MVFR

FM262000 01025G40KT 4SM RA OVC015 WS020/02050KT

Wind: 010° 25 kt G40
Visibility: 4 SM
Weather: Rain
Sky: OVC 1,500
Wind shear: 2,000 ft: 020° at 50 kt

Group by group

Groups in this period
Group	Meaning
`FM262000`	From From 26th 20:00 UTC, a new set of conditions replaces all earlier ones
`01025G40KT`	Wind Wind from 010° at 25 knots, gusting to 40 knots
`4SM`	Visibility Visibility 4 statute miles
`RA`	Weather Rain
`OVC015`	Cloud layer Overcast at 1,500 ft above the ground — a ceiling
`WS020/02050KT`	Low-level wind shear Wind shear: at 2,000 ft above the ground the wind is from 020° at 50 knots

Change periods show the prevailing wind, visibility, weather and sky they do not restate, so each category reflects what a pilot would plan on.

How a TAF is organized

A terminal aerodrome forecast covers the area within five statute miles of an airport's runways for 24 or 30 hours. The header gives the station, when it was issued and the valid period (2603/2706 means from the 26th at 03:00 to the 27th at 06:00 UTC). The prevailing forecast follows, then any change groups:

Change group	Example	Meaning
FM	`FM261400`	From the 26th at 14:00 UTC, all conditions change
BECMG	`BECMG 2604/2606`	A gradual change between 04:00 and 06:00 that then persists
TEMPO	`TEMPO 2606/2612`	Temporary fluctuations, each under an hour
PROB30, PROB40	`PROB40 TEMPO 2604/2606`	A 30 or 40 percent chance, optionally temporary
INTER	`INTER 2600/2603`	Australia: intermittent changes under 30 minutes each

The decoder shows every period with its own wind, visibility, weather, sky and flight category. Temporary and probability periods appear with a dashed border.

The worked example

The example is a real forecast for New York JFK issued on September 26, 2026: strong northeasterly winds gusting near 40 knots, rain, and a ceiling that lowers from 8,000 feet to 1,500 feet through the day, with low-level wind shear forecast from 06:00. The flight category moves from VFR to marginal VFR as the ceiling drops to 2,500 and then 1,500 feet.

How the decoder was checked

It was compared with the Aviation Weather Center's own parser on 400 real TAFs from around the world, covering more than 1,200 forecast periods, taken from its public data cache on September 26, 2026. On every well-formed forecast the two agree on each period's wind, gusts, visibility, cloud layers, wind shear and weather. The known exceptions are listed in the test notes: the Aviation Weather Center keeps only three cloud layers per period, and it reads one Navy remark as a wind. Forecasts with a malformed group show a caution instead of a guess.

Also decoded

NSW: no significant weather; the earlier weather ends.
CAVOK: visibility 10 km or more, no cloud below 5,000 feet or the minimum sector altitude, no significant weather.
TX/TN: forecast maximum and minimum temperatures with their times.
QNH2992INS: US military forecasts of the lowest altimeter setting.
AMD NOT SKED and AMD LTD TO CLD VIS AND WIND: limits on amendments.
Military turbulence (5-groups) and icing (6-groups).

A TAF is a forecast, not a promise. Compare it with the latest METAR before relying on it, and get an official briefing before flight.

Questions pilots ask

How do you read a TAF?

A TAF starts with the station, issue time and valid period, then the prevailing forecast. Change groups follow: FM starts a completely new set of conditions, BECMG a gradual lasting change, TEMPO temporary fluctuations, and PROB30 or PROB40 a 30 or 40 percent chance. The decoder lays each period out separately.

What does FM mean in a TAF?

From. FM261400 means that from the 26th at 14:00 UTC a new set of conditions replaces everything before it: wind, visibility, weather and clouds.

What is the difference between TEMPO and BECMG?

TEMPO describes temporary fluctuations, each lasting less than an hour and together covering less than half of the period. BECMG describes a change that happens gradually during the period and then persists.

What does WS020/02050KT mean?

Low-level wind shear: at 2,000 feet above the ground the wind is from 020° at 50 knots. Expect a significant change in wind between the surface and that height.

Why does a TEMPO period show visibility I did not see in that group?

Change groups only restate what changes. The decoder carries the prevailing wind, visibility, weather and sky into each TEMPO, PROB and BECMG period so its flight category reflects the full forecast conditions.