Invesco market watcher Kristina Hooper believes Wall Street should brace for trouble.

"We could see another about 10 percent sell-off, and it could happen relatively quickly or it could be a bit more gradual this time – sort of death by a thousand slashes potentially this fall," the firm's chief global market strategist said Tuesday on CNBC's "Futures Now." "I wouldn’t be surprised to see a significant sell-off in the second half."