Definition
Environmental conditions expected by a National Weather Service or Flight Service forecaster to be conducive to the formation of in-flight icing on aircraft, as published in an official aviation weather forecast such as an AIRMET, SIGMET, or area forecast.
Plain English
Weather conditions that an official forecast says are likely to cause ice to form on an aircraft in flight.
Context Anchor
Seen in preflight weather briefings, route planning, and aircraft operating limitations before deciding whether a flight can be made safely.
Derivation
‘Forecast’ comes from the Old English ‘fore’ (before) and ‘cast’ (to throw or project) — literally to project ahead. Here it means the icing is predicted by an official source, not yet observed.
Why Pilots Care
Knowledge of these conditions lets pilots choose safer altitudes, routes, or departure times to avoid loss of lift, added weight, and control problems.
Grounding Statement
Picture flying into a cold, wet cloud: even if you do not see ice yet, the forecast may be telling you that the ingredients for ice are there.
Intuition Check
Do not read forecast icing conditions as meaning ice is guaranteed or already on the airplane. It means the forecast calls for weather where ice could form, so the pilot must treat it as a real risk.
Example Sentence 1
The AIRMET indicated forecast icing conditions between 8,000 and 14,000 feet along our route, so we filed a lower altitude.
Example Sentence 2
The pilot delayed departure after the briefing revealed forecast icing conditions over the destination airport.