• an advance warning

Synonyms: harbinger, omen, augury, sign, signal, herald, indication, presage, portent, promise, prediction, forecast, premonition

• inform (someone) of a possible future danger or problem

Synonyms: warn, prewarn, warn in advance, give advance warning, give fair warning, give notice, advise, apprise, inform, harbinger, omen, augury, sign, signal, herald, indication, presage, portent, promise, prediction, forecast, premonition