Use 'forewarning' to suggest an event was surprising and not anticipated. The storm came without forewarning, leaving the town unprepared.
Pro Tip 2/3
Sense of Urgency
'Forewarning' often implies a need for immediate attention or action. The forewarning of the stock market crash caused investors to sell quickly.
Pro Tip 3/3
Hints of Future
Forewarning may be based on hints or signs of what will happen, not just explicit announcements. The silence was a forewarning of the bad news to come.