What Is a TAF? How to Read a Terminal Aerodrome Forecast

If you fly anywhere near a towered or busy airport, you read TAFs. They look like a string of code, but every group follows rules set out in NWS Instruction 10-813, the directive National Weather Service forecasters write them under [1]. This page decodes a full sample TAF from the FAA Aviation Weather Handbook group by group, explains the change groups, shows where TAFs mislead, and ends with where a TAF fits in a disciplined weather decision.

What does a TAF cover, and what doesn't it?

The Handbook's definition: "A TAF is a concise statement of the expected meteorological conditions significant to aviation for a specified time period within 5 SM of the center of the airport’s runway complex (terminal)." [2, para. 27.4] NWS Instruction 10-813 says the same, and defines the ring between 5 and 10 SM as the airport's vicinity (VC) [1, secs. 4 and 4.2].

A complete TAF includes "a forecast of surface wind (speed and direction), surface visibility, weather, obstructions to vision (if any), clouds (or vertical visibility into a surface-based obscuration), non-convective low-level wind shear (LLWS), and any expected significant change(s) to one or more of these elements" [1, sec. 4.2].

What it leaves out matters just as much. There is no temperature: "Temperature is not included in the NWS TAF", and the Handbook points to LAMP and MOS guidance for that [2, paras. 27.4 and 27.16]. It says nothing about the route between airports. And it doesn't show the forecaster's reasoning or confidence in words; that lives in the Aviation Forecast Discussion (AFD), which can "Provide additional aviation weather-related issues that cannot be encoded into the TAF, such as the reasoning behind the forecast" [2, para. 27.19].

When are TAFs issued, and how long do they last?

"Scheduled TAFs are typically issued four times daily, every six hours." [1, sec. 4.10] Each goes out 20 to 40 minutes before its valid period begins [2, para. 27.4.2.3]. The directive's schedule:

Source: NWS Instruction 10-813, Section 4.10 [1, sec. 4.10]. The directive's table also lists routine amendment times at 0300, 0900, 1500, and 2100 UTC.

• 24 or 30 hours. A TAF is "ordinarily 24 hours; however, there are FAA-specified international airports that require 30-hour TAFs" [1, sec. 4.2 and App. F].
• Who writes them. "TAFs are issued by NWS WFOs for nearly 700 U.S. airports." [2, para. 27.4.1] The NWS has 122 Weather Forecast Offices [2, para. 2.2.2.1.9].
• Always UTC. "The times in TAFs are stated in UTC." The letter Z after the issue time stands for Zulu [1, sec. 4.9].
• Amendments. Forecasters issue a TAF AMD promptly when amendment criteria are expected or have occurred, or when new information points to a different category, "especially in the 1- to 6-hour period" [1, sec. 4.7]. Some offices issue routine amendments three hours after each scheduled TAF, and the FAA Core 30 airports get scheduled amendments every three hours [1, secs. 4.10 and 4.11].
• The newest one wins. "The issuance of a new TAF cancels any previous TAF for the same time and location." [1, sec. 4.10] An amended TAF "supersedes and cancels the previous TAF" [2, para. 27.4.2.4]. A TAF COR fixes a mistake such as a typo or an incorrect time [1, sec. 4.6].
• Part-time airports. Where observations are not available around the clock, the TAF carries AMD NOT SKED: the forecaster "has enough data to issue a TAF but will not provide amendments" [1, sec. 4.13 and App. D4.1].

How do you read a TAF? A worked decode

A TAF always runs in the same order: report type, airport, issue time, valid period, then wind, visibility, weather, clouds, and wind shear if expected, followed by any change groups [2, Table 27-3][1, App. B]. Here is the Handbook's own sample TAF for Pierre, South Dakota (KPIR), printed exactly as it appears in the FAA Aviation Weather Handbook [2, para. 27.4.3]. It is an official teaching example, not a live forecast. Hover, focus, or tap any group for its meaning.

Scroll sideways to see the full line.

TAF
KPIR 111140Z 1112/1212 13012KT P6SM BKN100 WS020/35035KT
TEMPO 1112/1114 5SM BR
FM111500 16015G25KT P6SM SCT040 BKN250
FM120000 14012KT P6SM BKN080 OVC150 PROB30 1200/1204 3SM TSRA BKN030CB
FM120400 14008KT P6SM SCT040 OVC080 TEMPO 1204/1208 3SM TSRA OVC030CB

Official sample TAF, FAA Aviation Weather Handbook (FAA-H-8083-28B), Section 27.4.3 [2, para. 27.4.3]. The Handbook prints TEMPO and PROB30 on the same line as the FM group before them. In an issued NWS TAF, each FM group starts on a new line indented five spaces and each TEMPO group on a new line indented six; PROB30 stays on the line with the prevailing conditions [1, App. B2.9.2, B2.9.3, and B2.9.4].

Group by group. "Handbook meaning" is quoted exactly from FAA Aviation Weather Handbook 27.4.3; "Plain English" is ours, with the rule behind it cited.

Read as a whole: good visibility and a high ceiling at first, a morning spell of mist, then gusty southeast winds. After 0000Z there is a 30% chance of thunderstorms with a 3,000 ft ceiling and 3 SM, and after 0400Z thunderstorm spells are expected at times. On a flight-category scale, the thunderstorm periods drop into MVFR (ceiling 1,000 to 3,000 ft or visibility 3 to 5 miles) [3, para. 7-1-7]. The ceiling and visibility are only part of it: the directive says "LLWS is always assumed to be present in convective activity." [1, App. B2.8]

A second example: a frontal passage

NWS Instruction 10-813 uses this example for "rapid changes in wind associated with a frontal passage" [1, App. B2.4]:

Scroll sideways to see the full line.

TAF
KPIT 231732Z 2318/2418 23010KT 4SM -SHRA BKN030
     FM232200 28020G35KT P6SM OVC020
     FM232330 30015KT P6SM SCT060
     FM240500 30004KT P6SM SCT080=

Example from NWS Instruction 10-813, Appendix B2.4 [1, App. B2.4]. Not a live forecast.

• KPIT 231732Z 2318/2418: Pittsburgh, issued the 23rd at 1732Z, valid 1800Z on the 23rd to 1800Z on the 24th.
• 23010KT 4SM -SHRA BKN030: wind 230 at 10 knots, 4 SM in light rain showers (SHRA), broken ceiling at 3,000 ft.
• FM232200 28020G35KT P6SM OVC020: the front arrives at 2200Z. Wind swings to 280 at 20 gusting 35, visibility above 6 SM, overcast ceiling at 2,000 ft.
• FM232330 30015KT P6SM SCT060: at 2330Z, a change timed to the minute. FM times are given "to the nearest minute if the expected change can be forecast to that degree of accuracy" [1, sec. 4.12].
• FM240500 30004KT P6SM SCT080=: from 0500Z, light winds, 300 at 4 knots, with scattered clouds at 8,000 ft. The equal sign ends the TAF [1, sec. 4.8].

What do FM, TEMPO, and PROB30 mean?

The directive's PROB30 example: KROW 021726Z 0218/0318 30008KT 5SM HZ BKN030 followed by PROB30 0304/0306 27020G45KT 1SM TSRA OVC012CB [1, App. B2.4]. In words: wind 300 at 8 knots, 5 SM in haze, broken ceiling at 3,000 ft, with a 30% chance, from 0400Z to 0600Z on the 3rd, of a thunderstorm with rain, wind 270 at 20 gusting 45 knots, 1 SM visibility, and an overcast ceiling of 1,200 ft with cumulonimbus. That is IFR visibility (1 to less than 3 miles) [3, para. 7-1-7].

Source conflict, noted: the TEMPO entry in the directive's contraction list (Appendix A) and the AIM TAF key say less than one hour [1, App. A][3, para. 7-1-28], while the directive's TEMPO rules (Appendix B2.9.3) and the Handbook say one hour or less [1, App. B2.9.3][2, para. 27.4.2.10.2]. This page uses one hour or less. The AIM also still says NWS TAFs do not use PROB30 in the first 9 hours; the October 30, 2024 directive "Removed 9-hour PROB30 constraint in the first 9 hours" [1][3, paras. 7-1-28 and 7-1-29].

What about BECMG and PROB40?

You won't see either in an NWS TAF. The directive lists BECMG under "International Terminology and Forecast Groups Not Used in NWS TAFs" [1, App. E2], and the AIM says "The NWS does not use BECMG in the TAF." and "NWS does not use PROB 40 in the TAF." [3, para. 7-1-29] You can still meet them: all four joint-use airport examples in the Handbook use BECMG [2, para. 27.4.2.10.4], and for PROB40, "The U.S. military and international TAFs may use the PROB40 (40 percent chance) group as well." [2, para. 27.4.2.10.3] International TAFs may also use CAVOK, which the NWS does not use in U.S. domestic TAFs [2, para. 27.4.2.6].

What other codes will you see in a TAF?

Where can you see every TAF field and code?

What's the difference between a TAF and a METAR?

Where do TAFs mislead pilots?

• It is one airport. The forecast covers 5 SM around the runway complex [1, sec. 4]. A field 20 miles away, across a ridge or next to a lake, can have different weather, and the TAF doesn't claim otherwise.
• Most fields don't have one. TAFs cover nearly 700 U.S. airports [2, para. 27.4.1]. If yours isn't one, you are borrowing someone else's forecast.
• The first line isn't the whole story. A pleasant initial forecast can be followed by FM, TEMPO, or PROB30 groups that matter more for your arrival time. Read the whole TAF across your time window.
• TEMPO is not a footnote. TEMPO conditions are expected, with a greater than 50% probability; they are just brief [1, App. B2.9.3]. If a TEMPO condition is expected to last more than an hour, the directive calls for an FM group instead [1, App. B2.9.3].
• No WS group doesn't mean no shear near storms. The WS group covers only non-convective shear, and the directive says "LLWS is always assumed to be present in convective activity." [1, App. B2.8]
• Times are UTC. Misreading Zulu as local time shifts every change group by hours [1, sec. 4.9].
• Old TAFs linger. Always check that you have the newest TAF or amendment, since each one cancels the last [1, sec. 4.10].

What should you use when your airport has no TAF?

• Nearby TAF sites, with terrain in mind. Pick the ones that share your airport's exposure, not just the closest.
• The Aviation Forecast Discussion. The AFD describes conditions across the forecast area and the reasoning behind the TAFs [2, para. 27.19].
• LAMP. "The Localized Aviation MOS Program (LAMP) is a statistical system which provides forecast guidance for sensible weather elements." [4] The Handbook says it is available "at over 2,000 stations" and updated hourly [2, para. 27.16].
• MOS and NBM. MOS is statistical guidance built from computer model output [5]. The NBM is "a nationally consistent and skillful suite of calibrated forecast guidance based on a blend of both NWS and non-NWS numerical weather prediction model data and post-processed model guidance" [6].

Source conflict, noted: the Handbook describes LAMP as valid over a 25-hour period [2, para. 27.16], while NOAA's Meteorological Development Laboratory says LAMP now runs "out to 38 hours for most elements" [4]. This page relies on MDL, the office that runs LAMP, for the current length.

How do you use a TAF in a go/no-go decision?

The decision is yours as pilot in command. A TAF is one input, and a few habits make it a better one:

• Frame your window. Find every TAF period that overlaps your departure and arrival times, with a margin for delays, and take the worst one seriously.
• Compare to your personal minimums, not just legal ones. Flight categories give you a common scale: VFR, MVFR, IFR, and LIFR [3, para. 7-1-7].
• Treat TEMPO and PROB30 as real. A TEMPO is expected; a PROB30 thunderstorm is a stated 30% chance [1, Apps. B2.9.3 and B2.9.4]. Ask whether you have an out if it happens during your window.
• Write it down. A FRAT turns the hazards into a record: "The form used to record each hazard is known as a Flight Risk Assessment Tool (FRAT)." [9, ch. 3]

Flight categories from AIM 7-1-7 [3, para. 7-1-7].

Where does the TAF fit in a disciplined decision?

PlaneWX is decision support for general aviation pilots, built around one idea: "Fly like it's your job." Treat the weather decision the way a professional crew would, with the same process every time. That process is a loop: Brief, then FRAT, then Fly or Stay, then Debrief, with a Mentor if you want one. The TAF is one input to the Brief. Here's how PlaneWX handles it, as described in the help center [10]:

• Brief. The WX Score always runs against minimums: your own, or the defaults when you haven't saved any (VFR 3,000 ft and 5 SM, IFR 500 ft and 3 SM). It reads 75% and up as Favorable, 50 to 74% as Marginal, and under 50% as Unfavorable (WX Score). Ceilings and visibility shown reflect "the worst-case forecast from TAF periods covering your departure/arrival window" (Understanding Briefings).
• Inside 12 hours. A server-side pre-flight check runs against TAF data; a hard-limit exceedance sets the score to 0%. It looks at PROB30 periods (PROB40 on U.S. military and some international TAFs) for thunderstorms, freezing rain, and low visibility, and at TEMPO periods with TS, FZRA, or SN (How Scoring Works, WX Score).
• Further out. A distant TAF thunderstorm probability weighs less than a near-term one: about 40% of the full penalty at 36 hours or more, 100% inside 6 hours. From 12 to 72 hours out, the score leans on TAF, then MOS (MAV or MEX), then NBM, then model data (WX Score). Beyond 12 hours a 25% floor applies, unless a covering TAF already shows wind shear or crosswind over your hard limit (How Scoring Works).
• No TAF. PlaneWX uses a terrain-aware proxy TAF from a nearby airport (up to 35 SM in flat terrain, 25 rolling, 20 complex, 12 mountain) and the briefing shows the proxy airport code and distance; you can change the pick (Weather Decisions, Weather Proxies).
• FRAT. The flight risk assessment opens within 4 hours of departure. Weather and the WX Score appear as hints, and your own ratings drive it (FRAT).
• Fly or Stay. "PlaneWX never recommends GO or NO-GO. You make the call as PIC." (The Risk Loop)
• Debrief. Self Debrief looks back at the flight. It is a PlaneWX Labs feature for Pro Plus and doesn't change your WX Score. A mentor sees the same briefing and FRAT, and the debrief only if you grant it (The Risk Loop).

The help center is plain about the limits: "PlaneWX is not a substitute for a complete, independent pre-flight weather briefing. Pull one from a source you already trust before you fly." (The Risk Loop)

See how a PlaneWX briefing reads the TAF for your next trip, or read how the WX Score works.

This page explains published NWS and FAA guidance. The TAFs shown are official teaching examples from FAA and NWS documents, not live forecasts. Always get a current briefing before you fly.