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

A Terminal Aerodrome Forecast (TAF) is a forecast of the expected weather within about five statute miles of a single airport, typically valid for a 24-hour window (30 hours at larger airports) and issued four times a day. While a METAR tells you what the weather is doing right now, the TAF tells you what the airport will look like when you arrive — making it the single most important weather product for flight planning. The skill isn’t just reading the codes; it’s finding your arrival time on the forecast and deciding whether to go.

What is a TAF and how is it different from a METAR?

The METAR is the truth on the ground right now. The TAF is the educated guess about the future at one specific airport.

Here’s the part nobody explains clearly: a TAF is not a regional forecast. It covers only the weather within roughly five statute miles of the center of the runway complex. The weather 40 miles away can be a completely different world.

A TAF also has a birthday and an expiration date. Most cover 24 hours, larger airports run 30 hours, and new ones are issued roughly every six hours. Before you trust a single word of it, you need to know both when it was issued and how long it’s valid.

How do I read the header of a TAF?

Let’s build a real example and translate it as we go, starting with KMCI (Kansas City). The leading K simply tells you the station is in the contiguous United States.

Next comes a six-digit issuance time followed by Z, such as 121738Z. Break it apart:

• 12 — the day of the month (the 12th)
• 1738 — the time issued (17:38)
• Z — Zulu, or Coordinated Universal Time

Everything in aviation weather lives in Zulu time. Convert it to your local time on the ground, in pencil, before you’re doing mental math at altitude with a headache.

What does the valid period in a TAF mean?

After the issuance time comes the valid period, shown as two groups separated by a slash: 1218/1318.

• 1218 — the forecast becomes valid on the 12th at 1800Z
• 1318 — it expires on the 13th at 1800Z

That’s your 24-hour window. If your arrival time falls outside the valid period, the TAF is telling you nothing about your flight. Pilots routinely plan a morning flight while reading last night’s expired forecast — the numbers look great and they’re completely irrelevant.

How do I decode the weather conditions in a TAF?

The good news: a TAF uses the same vocabulary as the METAR. The forecast opens with the prevailing conditions, read in a fixed order.

Wind comes first as five digits plus KT: 24012KT means wind from 240 degrees at 12 knots. Note that TAF and METAR winds are referenced to true north, not magnetic — a common gotcha. A G signals gusts, so 24018G30KT is wind from 240 at 18 gusting 30. The moment you see a gust spread, start thinking about crosswind components and your personal limits.

Visibility comes next. P6SM means visibility greater than six statute miles — the “P” stands for plus. When that number drops below six, pay close attention.

Sky condition uses standard shorthand with a three-digit height in hundreds of feet above the airport:

• SKC / CLR — clear
• FEW — few
• SCT — scattered
• BKN — broken
• OVC — overcast

So BKN035 is a broken layer at 3,500 feet. Remember: only broken or overcast officially counts as a ceiling — few and scattered do not.

Put it together — 240 at 12, six miles and better, broken at 3,500 — and that’s a perfectly nice flying day to start. But the start isn’t the story. The story is what changes.

What do FM, BECMG, and TEMPO mean in a TAF?

The TAF describes change with three keywords you have to know cold.

FM (FROM) signals a real, lasting change. FM2300 means: starting at 2300Z, throw out everything before this and replace it with an entirely new picture that sticks until the next group. Treat a FROM line as a brand-new forecast that begins at that time.

BECMG (BECOMING) is gentler and comes with a time range, like BECMG 0204. The change happens gradually between 0200Z and 0400Z, and once complete, it stays. Think of a cold front sliding through, the wind slowly clocking around over a couple of hours.

TEMPO (TEMPORARY) is the one that trips people up. It comes with a time range and describes conditions expected to come and go — each occurrence lasting less than an hour and totaling less than half the period.

Here’s the trap: pilots see a low ceiling under a TEMPO and wave it off as “just temporary.” Don’t. For planning, treat a TEMPO condition as something that absolutely can be happening the moment you arrive. If the TAF says TEMPO 2SM BKN008 in mist, plan as if you’ll roll up to 800 feet and two miles — because you might.

How does reading a TAF change a real go/no-go decision?

Picture it. You’re a fresh private pilot flying a Cessna 172 two hundred miles to see a friend, planning to arrive around 2300Z. The prevailing line looks gorgeous — clear, light winds, great visibility. You’re already mentally packing the airplane.

But at the bottom sits one line: FM2230. From 2230Z, wind from the south at 15 gusting 25, visibility four miles in mist, broken at 1,200.

That FROM group starts 30 minutes before you plan to land, and it’s not a fleeting TEMPO — it’s the new reality, and it stays. The airport you imagined as clear and calm is forecast to be a 1,200-foot ceiling, four miles of murk, and a gusty crosswind right as you show up.

That single line should rewrite your plan: leave earlier to beat the change, pick a different destination, build in a solid alternate and extra fuel — or just don’t go. But you only get to make that call if you read the line instead of skimming for “clear” at the top.

This is exactly what the Airman Certification Standards expect on a checkride. The examiner doesn’t want you sounding out symbols like a first-grader reading words; they want you to interpret the weather and connect it to your airplane, your experience, and your personal minimums. Reading the TAF is the easy part. Deciding what to do about it is the skill.

What’s the right way to use a TAF when flight planning?

Follow these steps on your very next flight:

1. Check the valid period first. If your flight doesn’t fall inside the window, stop and find a current forecast. An expired TAF is worse than no TAF because it gives false confidence.
2. Read the forecast for your exact arrival time. Don’t stop at the prevailing line. Walk down through every FROM, BECMG, and TEMPO and ask: is this group active when I’ll be airborne or on approach?
3. Respect the TEMPO. Plan for the worst version it describes, not the best. If you’ve got the fuel and alternate to handle the bad version, you’re in good shape.
4. For untowered fields with no TAF, use the nearest one — with a margin of doubt. That five-mile bubble means the weather can differ sharply over distance. Treat a nearby TAF as a clue, not a guarantee, and back it up with the area forecast discussion and any PIREPs.
5. Read the TAF together with the METAR, never instead of it. If the current METAR is already worse than the TAF predicted, that’s a giant red flag that the forecast is behind the actual weather — and conditions may keep deteriorating faster than anyone wrote down.

There’s no shame in being deliberate. The pilots who get hurt by weather are almost never the ones who read the forecast too carefully.

Key Takeaways

• A TAF forecasts weather within five statute miles of one airport, usually valid 24 hours and reissued every six hours.
• Always check the valid period first — an expired TAF gives dangerous false confidence.
• FM is a lasting change, BECMG is a gradual transition, and TEMPO is a come-and-go condition you should plan to encounter on arrival.
• Only broken (BKN) and overcast (OVC) layers count as a ceiling; TAF winds reference true north.
• The real skill is making a sound go/no-go decision for your arrival time — not just decoding the symbols.