Related Clues:

• Seer's sign
• Warning sign
• Telltale sign
• Sign of things to come
• Forewarning
• Sign of foreboding
• Dark clouds on the horizon, say
• Portentous event
• Dark clouds, say
• Evil sign
• Hooting owl, maybe
• Sense
• *Eclipse ... black cat ... future
• Warning
• Writing on the wall