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It is commonly cited that a Terminal Aerodrome Forecast (TAF) is good for 5 statute miles around the airport it's forecasting for, but where is that 5 statute mile specification? I looked in the FAR/AIM and the and I could only find information about decoding them and when they were updated.

What publication specifies that the TAF covers a 5 statute mile radius (in the US)?

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I've found it in two official US government documents where it describes the 5 SM radius for TAFs.

One from NOAA:

NWS TAFs consist of the expected meteorological conditions significant to aviation at an airport for a specified time period. For the U.S., this is the area within five (5) statute miles (SM) of the center of an airport’s runway complex.

Source: National Weather Service Instruction 10-813. November 18, 2020. Operations and Services. Aviation Weather Services, NWSPD 10-8. Terminal Aerodrome Forecasts. p. 5.

And one from the FAA in AC 00-45H - Aviation Weather Services - Change 2 on page 5-84 (emphasis added):

5.13 Terminal Aerodrome Forecast (TAF).

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). The TAFs use the same weather codes found in METAR weather reports (see paragraph 3.1) and can be viewed on https://www.aviationweather.gov.

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  • $\begingroup$ That is consistent with the definition of "vicinity" at ICAO level, in Annex 3, §4.4.2.7: "Vicinity— Between approximately 8 and 16 km of the aerodrome reference point and used only in METAR and SPECI with present weather in accordance with the template shown in Table A3-2". I guess 8 km comes from the conversion of 5 sm. $\endgroup$
    – mins
    Jul 8, 2021 at 15:53
  • $\begingroup$ In the U.S., "vicinity" in the METAR or TAR is weather between 5 and 10 SM. $\endgroup$
    – wbeard52
    Jul 13, 2021 at 13:24
  • $\begingroup$ In weather reports (TAF and METAR) according to the AIM (faa.gov/air_traffic/publications/media/AIM.pdf) the abbreviation VC means Vicinity, but not at aerodrome. In the US METAR, 5 to 10 SM from the point of observation. In the US TAF, 5 to 10 SM from the center of the runway complex. Elsewhere, within 8000m. (Fig 7-1-22) However, my question was, "where is it specified that TAFs cover 5 SM?" Which I found in the answer above. It makes sense then, that you'd assume the weather reported in the TAF was within that 5 SM radius, and if not, the TAF uses the qualifier VC. $\endgroup$
    – Canuk
    Jul 14, 2021 at 1:00

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