Editing Terminal aerodrome forecast (section)

== Issuance, amendment and cancellation ==
In the United States, TAFs are issued for nearly 700 airports. Most of them provide a 24-hour forecast for the airport, with some major airports forecasting for 30 hours into the future.<ref name="AWH" /> TAFs are issued at least four times a day, every six hours, for major civil airfields: 0000, 0600, 1200 and 1800 UTC,<ref>{{Cite web|url=https://www.nws.noaa.gov/directives/sym/pd01008013curr.pdf|title=National Weather Service Instruction 10-813}}</ref> and generally apply to a 24- or 30-hour period, and an area within approximately {{Convert|5|smi|lk=in|spell=in}} (or {{Convert|5|NM|km}} in Canada) from the center of an airport runway complex. TAFs are issued every three hours for military airfields and some civil airfields and cover a period ranging from 3 hours to 30 hours.

Different countries use different change criteria for their weather groups. In the United Kingdom, TAFs for military airfields use [[colour state]]s as one of the change criteria. Civil airfields in the UK use slightly different criteria.

If information sources, such as surface observations, are missing, unreliable, or not complete, forecasters
will <code>append AMD NOT SKED</code> to the end of a TAF. This code indicates the forecaster
has enough data, using the total observation concept, to issue a forecast, but will not provide updates. This
allows airport operations to continue using a valid TAF. In rare situations where observations have been missing for extended periods of time (i.e., more than one TAF cycle of 6 hours) and the total observation concept cannot provide sufficient information, the TAF may be suspended by the use of <code>NIL TAF</code>.<ref>{{Cite AWH|year=2024|chapter=27|page=21}} {{PD-notice}}</ref>