Definition
Weather information that predicts atmospheric conditions for a specified period in the future, based on analysis of current observations, computer models, and meteorologist interpretation. Forecast data has a defined valid time window during which it is intended to be used, and it expires once that window closes.
Plain English
Weather predictions for a future time. Each forecast is good for a set period and should not be used after it expires.
Context Anchor
Seen when checking the age and expiration of aviation weather products during preflight planning.
Derivation
Forecast comes from the older English fore- meaning 'before' and cast meaning 'to throw or plan ahead.' Literally, it means 'thrown ahead' — a prediction projected forward in time. This helps separate it from current observations, which describe what is happening now.
Why Pilots Care
Flight planning depends on weather expected at the time of departure, en route, and arrival — not the weather happening now. Using a forecast that is out of date, or applying it to a time outside its valid window, can lead to serious mismatches between expected and actual conditions.
Intuition Check
Forecast data is not the same as current observed weather. It is a prediction, and it only helps if it applies to the time and place you are planning for.
Example Sentence 1
Before departure, the pilot reviewed the forecast data for the destination to confirm conditions would still be VFR at the planned arrival time.
Example Sentence 2
Updated forecast data replaced the earlier package once the original product reached its expiration time.