Are There Any Amendment Criteria for a TAF?

When there’s a discrepancy, an aviation weather forecaster can make an update.

Scott Dennstaedt, Ph.D

Wednesday, January 04, 2023 at 01:34 PM ET

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When there’s a discrepancy, an aviation weather forecaster can make an update. [Credit: iStock]

Key Takeaways:

TAF amendments are unscheduled updates issued by local NWS Weather Forecast Offices when current or expected weather conditions (ceiling, visibility, wind, weather) significantly deviate from the forecast, and these changes are anticipated to last for 30 minutes or more, or to shift the airport's flight category.
Forecasters are assisted by AvnFPS software, which continuously monitors observations against the TAF and highlights elements nearing or exceeding specific amendment thresholds.
Amendment criteria include changes in categorical flight conditions (VFR, MVFR, IFR, LIFR), the occurrence or non-occurrence of forecasted or unforecasted significant weather (e.g., thunderstorms, freezing precipitation, low-level wind shear), and notable differences in wind speed (≥ 10 knots) or gusts.
Some high-traffic airports (e.g., Chicago, Atlanta, NYC) receive more frequent 2-3 hourly updates, which are treated as amendments whether a specific criterion was met or not.

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Question: Can you tell me if there are any amendment criteria for a TAF (terminal aerodrome forecast)? If so, what are they and how are they applied?

A. Most of the official aviation weather forecasts you will get on a standard briefing or via your favorite heavyweight aviation app or website are issued by aviation meteorologists located at the Aviation Weather Center (AWC) in Kansas City, Missouri. This includes graphical AIRMETs (G-AIRMETs), SIGMETs (WS) and convective SIGMETs (WST). Terminal aerodrome forecasts or TAFs, however, are not issued by the AWC nor are they issued by Flight Service; they are issued by forecasters physically located at your local NWS Weather Forecast Offices (WFO) throughout the United States and its territories shown below. The meteorologists at the local WFOs are very familiar with any local weather effects and have the best opportunity to produce a quality forecast for aviation.