Decoding the TAF and the terminal forecast that tells you what the airport will look like when you get there

The Terminal Aerodrome Forecast (TAF) tells pilots what the weather will do at an airport, making it arguably more important than the METAR for cross-country planning. While METARs report current conditions, the TAF forecasts what the sky will look like when you arrive — and knowing how to decode every line, especially the change groups, is essential for safe go/no-go decisions.

What Is a TAF and Why Does It Matter More Than the METAR?

A METAR is a snapshot of current weather. A TAF is a forecast, typically covering the next 24 hours (30 hours at major airports). If you are flying a cross-country, the current weather at your destination is almost irrelevant — you need to know what it will be when you get there. That is what the TAF provides.

How Do I Read the TAF Header?

Every TAF begins with a standard header containing three pieces of information:

1. The identifier “TAF” — confirms the product type.
2. The station identifier — a four-letter ICAO code (e.g., KABQ). In the continental United States, the leading “K” designates a CONUS station.
3. The issuance time — six digits followed by “Z.” The first two digits are the day of the month; the next four are the time in UTC (Zulu). For example, 210940Z means the forecast was issued on the 21st at 0940Z.

Immediately after the issuance time comes the valid period, formatted as two four-digit day/time groups separated by a slash. 2112/2212 means the forecast covers from the 21st at 1200Z through the 22nd at 1200Z.

Check the valid period first. If your arrival falls outside this window, the TAF has nothing useful to tell you.

How Do I Decode Winds in a TAF?

Wind is reported as five or six digits followed by KT (knots):

• The first three digits are wind direction in degrees true (not magnetic).
• The next two or three digits are speed in knots.
• A G indicates gusts. Example: 27015G25KT means wind from 270° true at 15 knots, gusting to 25.

Common variations:

• 00000KT — calm winds
• VRB03KT — variable at 3 knots

Important detail: TAF winds use true north, not magnetic north. When comparing to runway headings on approach plates, account for magnetic variation.

How Do I Read Visibility and Weather in a TAF?

Visibility in U.S. TAFs is reported in statute miles (SM):

• 6SM — six statute miles
• P6SM — greater than six miles (the “P” means “plus”)
• 1/2SM or 1/4SM — fractional miles, indicating significantly reduced visibility

Weather codes use the same format as METARs:

• -RA — light rain
• +TSRA — heavy thunderstorms with rain
• BR — mist
• FG — fog

If no significant weather is expected, this group is omitted entirely.

Cloud cover follows standard categories — FEW, SCT, BKN, OVC — each with a three-digit height in hundreds of feet AGL. BKN025 means broken at 2,500 feet. OVC010 means overcast at 1,000 feet. SKC means sky clear.

What Are TAF Change Groups and Why Are They Critical?

Change groups are where the TAF becomes a genuine planning tool. The forecaster does not expect conditions to remain static for 24 hours. There are four types of change indicators:

FM (From)

FM followed by a six-digit date-time group means a complete replacement of the previous forecast. Everything — wind, visibility, clouds — resets. Think of it as a clean slate. FM212000 means starting at 2000Z on the 21st, the entire forecast changes to the new conditions listed.

BECMG (Becoming)

BECMG indicates a gradual transition between two time points. BECMG 2114/2116 means conditions will slowly shift between 1400Z and 1600Z on the 21st, with the new conditions fully established by the end of that window. Think of it as a slow fade — ceilings lower gradually, not all at once.

TEMPO (Temporary)

TEMPO means conditions will temporarily fluctuate to the stated weather for less than half the indicated time period. Example: TEMPO 2118/2122 -SHRA BKN020 means between 1800Z and 2200Z, expect occasional light rain showers and broken clouds at 2,000 feet — but not continuously.

Do not ignore TEMPO groups. If a TEMPO condition puts ceilings or visibility below VFR minimums, you need a plan. “Temporary” does not mean it will not be happening exactly when you arrive.

PROB (Probability)

PROB30 or PROB40 followed by conditions indicates a percentage chance of those conditions occurring.

• PROB30 — relatively low probability
• PROB40 — warrants serious attention

If you are a VFR pilot and see PROB40 for thunderstorms or IFR conditions during your arrival window, reconsider whether the flight is happening today.

How Should I Use the TAF for Cross-Country Planning?

Consider this scenario: You depart at 1400 local for a two-hour flight. The TAF’s initial line shows winds 180 at 8, visibility greater than 6 miles, scattered clouds at 4,500 feet. Looks perfect.

But a BECMG group between 2000Z and 2200Z shows winds shifting to 210 at 15 gusting 22, visibility dropping to 3 miles in mist, broken ceiling at 1,200 feet. That window lines up with your estimated arrival.

The VFR weather in the initial forecast will not be there when you land. This is why you read the entire TAF — not just the first line. The opening conditions describe the present. The change groups describe your future.

When Are TAFs Issued and Which Airports Have Them?

TAFs are issued four times daily at most U.S. airports: approximately 0040Z, 0640Z, 1240Z, and 1840Z. They can be amended at any time when conditions change significantly. If you briefed two hours ago and weather is moving fast, pull a fresh TAF before departure.

Not every airport receives a TAF. Smaller fields often lack terminal forecasts. In those cases, use the TAF for the nearest reporting airport and supplement with the Graphical Forecast for Aviation (GFA) tool. Recognize that you are extrapolating — weather 30 miles away may differ significantly, especially near hilly terrain or large bodies of water.

What Is the Best Practice for Briefing TAFs?

Pull TAFs for three locations: your departure airport, your destination, and at least one alternate or waypoint along the route. Read each one completely. Find the change groups that overlap with your expected time at each location, and ask: If the worst-case conditions in these change groups are what I find, can I still land safely?

If the answer is no — or even maybe — have an alternate plan before you leave the ground, not after you are 60 miles out with the fuel gauge dropping.

Key Takeaways

• The TAF forecasts future weather at an airport, typically covering 24 hours — making it essential for any flight where you will not arrive immediately.
• Always check the valid period first to confirm the TAF covers your arrival time.
• TAF winds use true north, not magnetic — account for variation when comparing to runway headings.
• Read every change group (FM, BECMG, TEMPO, PROB) — the initial forecast line only describes conditions at the start of the valid period.
• TEMPO and PROB40 conditions demand a plan — temporary or probabilistic does not mean irrelevant to your flight.