Reading a TAF and the coded forecast that tells you what your destination will look like before you get there

The Terminal Aerodrome Forecast (TAF) is the coded weather product that tells you what conditions will look like at your destination airport hours before you arrive. While a METAR reports current conditions, the TAF forecasts what’s coming — and for any cross-country flight, the TAF at your destination is arguably more important than the METAR at your departure point. The weather you’re leaving doesn’t matter nearly as much as the weather you’re arriving into.

What Is a TAF and Why Does It Matter?

A TAF is issued by forecasters at the Aviation Weather Center and provides a predicted weather picture for a specific airport over a 24- to 30-hour period. It covers wind, visibility, weather phenomena, and cloud layers — everything you need to assess whether your destination will be flyable when you get there.

One critical detail many students miss: TAFs are only issued for airports with weather reporting capability. If you’re flying into a small grass strip with no weather station, you’ll need to use the TAF from the nearest reporting airport and make educated guesses about local conditions.

How Do I Read the TAF Header?

Every TAF starts with a few standard groups:

• TAF or TAF AMD — The label. “AMD” means the forecast has been amended because conditions shifted faster than expected. An amended TAF is a signal that the atmosphere is being unpredictable, so pay extra attention.
• Station identifier — Four letters (e.g., KJFK, KOSH, KLAS) identifying the airport.
• Issuance time — A six-digit group. The first two digits are the date, the next four are the time in Zulu. For example, 051730Z means the 5th of the month at 1730Z. If the TAF was issued 12 hours ago, the atmosphere has had half a day to change.
• Valid period — Two four-digit groups separated by a slash (e.g., 0518/0618). This means valid from the 5th at 1800Z through the 6th at 1800Z. If your estimated arrival falls outside this window, you need a newer TAF.

How Do I Decode the Wind, Visibility, and Weather Groups?

Wind is reported as five or six digits followed by “KT.” The first three digits give direction in degrees true, the next two or three give speed in knots. Gusts are indicated by the letter G followed by gust speed. For example, 27015G25KT means wind from 270 degrees at 15 knots, gusting to 25. Calm winds appear as 00000KT, and light variable winds as VRB03KT.

Those gust values should feed directly into your personal minimums. If the TAF shows gusting to 30 knots and you’re flying a Cessna 172 with 40 hours in your logbook, make that decision on the ground — not on a two-mile final getting kicked around.

Visibility is reported in statute miles. P6SM means greater than six statute miles. 3SM means three miles. 1/2SM means half a mile. If you see a number less than three in a TAF and you’re a VFR pilot, that’s a major red flag.

Weather phenomena use the same codes as METARs: RA (rain), SN (snow), BR (mist), FG (fog), TS (thunderstorms). Intensity qualifiers: minus sign (−) means light, plus sign (+) means heavy, no sign means moderate. +TSRA means heavy thunderstorms with rain. No weather group at all means no significant weather is expected.

How Are Cloud Layers Reported in a TAF?

Cloud layers appear as groups like SCT025, BKN040, OVC060 — scattered at 2,500 feet, broken at 4,000, overcast at 6,000. These altitudes are in hundreds of feet above ground level (AGL), not MSL.

This distinction is critical. A broken ceiling at 4,000 feet AGL at a field with an elevation of 500 feet means the clouds sit at 4,500 feet MSL on your altimeter. If you’re determining whether you can legally get in there VFR, you need to do that math.

What Do FM, TEMPO, BECMG, and PROB Mean?

These change groups describe how conditions will evolve over the forecast period. Understanding the difference between them is essential — and it’s something the ACS expects you to explain during your oral exam.

FM (From) — A complete forecast replacement at a specific time. FM2100 means at 2100Z, everything resets: new wind, new visibility, new clouds. Think of it as drawing a line across the page and starting fresh. Forecasters use FM when they expect a definitive change, like a cold front passage.

TEMPO (Temporary) — Brief fluctuations from the prevailing conditions within a time window. TEMPO 0520/0600 means between 2000Z and 0600Z, conditions may temporarily dip to what follows — perhaps visibility dropping to two miles in mist for 20 or 30 minutes at a time, while the prevailing condition remains five miles. The critical question: can you safely get in there if TEMPO conditions are in effect when you arrive?

BECMG (Becoming) — A gradual transition over a specified window. BECMG 0514/0516 means conditions will slowly shift to the new state between 1400Z and 1600Z. By the end of that window, the new conditions are expected to prevail. Think of it as a slow fade — the exact timing within the window is uncertain.

PROB (Probability) — A percentage chance of conditions occurring. You’ll only see PROB30 or PROB40 in a TAF. If the forecaster thinks there’s more than a 40% chance, they’ll use TEMPO or BECMG instead.

How Should I Use a TAF in My Flight Planning?

Reading the codes is only half the job. The real skill is running the TAF through your specific flight plan. Here’s a practical scenario:

You’re planning a 170-nautical-mile cross-country with an estimated time enroute of 1 hour 40 minutes. Departure at 1500Z, arrival around 1640Z. The TAF at your destination starts with beautiful VFR — winds 180 at 8 knots, visibility greater than 6, scattered at 5,000.

But then you see: BECMG 1500/1700 BKN015 3SM BR

Between 1500Z and 1700Z, conditions are expected to deteriorate to a broken ceiling at 1,500 feet AGL and 3 miles in mist. Your arrival at 1640Z falls right in the middle of that transition. The ceiling might already be down — or it might still be fine. The forecaster is telling you the change is coming, but the exact timing is uncertain.

Three steps to work this problem:

1. Check the METAR at your destination right before departure. Is it already deteriorating earlier than forecast? If so, conditions may be worse than predicted by the time you arrive.
2. Identify a VFR diversion point within about 30 minutes of your destination that has its own TAF showing better conditions during your arrival window.
3. Set a personal go/no-go gate before you take off. Decide that if the ceiling at your destination is below 2,000 feet at your fuel stop, you divert — no negotiation. Make that decision at the kitchen table, not in the air.

Why You Should Keep Checking

TAFs are forecasts, not guarantees. A forecaster is making an educated prediction based on models, observations, and experience. Sometimes they’re spot-on. Sometimes conditions change faster or slower than expected.

Check the TAF the night before. Check it again the morning of your flight. Check the METAR at your destination before departure. If you have flight following or Flight Service on frequency, check again enroute. The TAF is your best available prediction, but treat it as one piece of a bigger picture that includes METARs, PIREPs, and your own eyes out the window.

Key Takeaways

• The TAF forecasts future conditions at a specific airport over a 24- to 30-hour window — it’s essential for any cross-country flight.
• Cloud heights in a TAF are AGL, not MSL — you must add field elevation to determine where clouds sit on your altimeter.
• Know the change groups: FM replaces the entire forecast, TEMPO is a brief fluctuation, BECMG is a gradual transition, and PROB indicates a 30–40% chance.
• Run the TAF through your specific flight plan — match forecast conditions to your estimated arrival time, aircraft, and experience level.
• Keep checking throughout your flight — TAFs are predictions, not promises. Cross-reference with METARs and PIREPs for the full picture.