Related Clues:

• Having heightened senses
• Sometimes it's golf ball size
• APB, for one
• Give kudos to
• A serious one may be red
• Storm warning
• Wave to, as a taxi
• Cloud output, sometimes
• Signal, as a taxi
• Emulate Paul Revere
• Precipitation type
• "Fore!" for one
• Flag down a cab
• Give a heads-up to
• Solid precipitation