Definition
A weather pattern (such as a front, low-pressure area, line of thunderstorms, or area of icing) that meteorologists predict will affect a given area during a specified time period, based on current observations and atmospheric models.
Plain English
Weather that hasn't happened yet but is expected to arrive, based on what forecasters are seeing build up in the atmosphere.
Context Anchor
Pilots encounter this term during preflight planning, weather briefings, and risk decisions about whether to go, delay, change route, or cancel.
Derivation
Forecast' comes from Old English fore- ('before') and casten ('to throw or plan'). Literally 'to plan ahead.' In aviation, it refers to weather conditions thrown ahead in time -- predicted, not yet observed.
Why Pilots Care
Allows pilots to anticipate and mitigate weather-related risks before departure.
Grounding Statement
A clear sky at your airport does not remove the risk if a larger weather pattern is predicted to arrive during your flight window.
Intuition Check
Do not assume a forecast weather system means the bad weather is already overhead. It means an organized weather pattern is predicted to affect the area during the relevant time.
Example Sentence 1
During preflight planning, the pilot noted a forecast weather system moving in from the west and decided to depart two hours earlier to stay ahead of it.
Example Sentence 2
Understanding the forecast weather system helped the instructor explain how fronts affect visibility during cross-country training.