TAF and METAR Decoding

AIM ¶ 7-1-28 — TAF and METAR Decoding

Decode TAF and METAR reports with the official AIM 7-1-28 key. Learn wind, visibility, weather codes, FM, TEMPO, BECMG, and PROB groups for checkride prep.

In Plain English

AIM 7-1-28 provides the official decoding key for reading TAFs (Terminal Aerodrome Forecasts) and METARs (Aviation Routine Weather Reports) — the two backbone weather products every pilot must understand.

Key elements decoded include:

Report type: TAF (routine), TAF AMD (amended), METAR (hourly), SPECI (special)
Location: 4-letter ICAO identifier (e.g., KPIT)
Time: All times in UTC (Z), with a 2-digit date and 4-digit time
TAF valid period: 24 or 30 hours, shown as date/hour pairs (e.g., 0918/1024)
Wind: True-north direction, speed in knots, with gusts (G) as needed; 00000KT = calm
Visibility: Statute miles in the U.S.; P6SM means greater than 6 SM
RVR: Runway visual range in feet (e.g., R28L/2600FT)
Sky cover: SKC, FEW, SCT, BKN, OVC with cloud bases in hundreds of feet; CB and TCU noted
Temp/dewpoint: In °C, M prefix for negative
Altimeter: A### in inches Hg (Q in hPa elsewhere)
Change groups: FM (rapid change), BECMG (gradual), TEMPO (brief <1 hr), PROB30/40 (probability)
Weather qualifiers: "-" light, "+" heavy, VC vicinity; descriptors like TS, SH, FZ; phenomena like RA, SN, BR, FG

Why it matters: accurate weather decoding drives go/no-go decisions, alternate planning, and IFR fuel reserves. The AIM also notes that ceiling is the lowest BKN/OVC layer or vertical visibility, even though it's not labeled as such in the report.

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AIM Source Text

FAA AIM ¶ 7-1-28

FIG 7-1-22 Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Front) FIG 7-1-23 Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Back)

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Oral Exam Questions a DPE Might Ask

Q1What does the FM group in a TAF mean, and how does it differ from BECMG?

Per AIM 7-1-28, **FM (FroM)** indicates a rapid, significant change expected at a specific date/hour/minute, and each FM starts on a new line indented 5 spaces. **BECMG (BECoMinG)** indicates a gradual change expected during a window between a beginning and ending date/hour. FM is essentially instantaneous; BECMG is a transition period.

Q2How is ceiling determined from a METAR, and what cloud cover symbols define it?

Per AIM 7-1-28, ceiling is not explicitly labeled in the report. It is defined as the **lowest broken (BKN, 5/8–7/8) or overcast (OVC, 8/8) layer, or the vertical visibility (VV)** when the sky is obscured. SKC, FEW, and SCT layers do not constitute a ceiling.

Q3Decode the visibility and weather group '3/4SM TSRA' and the qualifier '+TSRA'.

Per AIM 7-1-28, **3/4SM** is prevailing visibility of three-quarters of a statute mile. **TSRA** combines the descriptor **TS (Thunderstorm)** with the precipitation **RA (Rain)** — a thunderstorm with rain. The **"+"** in **+TSRA** is an intensity qualifier meaning **heavy**, so +TSRA is a heavy thunderstorm with rain.

Related Paragraphs in Chapter 7

¶ 7-1-1

NWS Aviation Weather Program

¶ 7-1-10

Weather Observing Programs

¶ 7-1-11

Weather Radar Services

¶ 7-1-12

ATC Weather Avoidance

¶ 7-1-13

Runway Visual Range

¶ 7-1-14