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Weather servicesQuestion 374 of 934

In a TAF, when does the forecaster use FM?

  1. When a short change is expected to last less than one hour
  2. When a 30 or 40 percent chance of storms is expected
  3. When a rapid, significant change is expected within an hour
  4. When the forecaster corrects an error in the forecast
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Correct answer: When a rapid, significant change is expected within an hour

TEMPO is used for temporary changes that last less than one hour.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 13: Aviation Weather Services — Terminal Aerodrome Forecasts, page 319

Practice weather services

Questions last reviewed: 18 October 2026