Hijack the Seas: Tsunami (Cassandra Palmer, #14)

Cassie Palmer, once the chief seer of the supernatural world, is out of a job. She's also out of time her time. Thrown fifty years into the future by a spell she doesn't understand, she finds herself sans power, sans allies, and sans a plan except to get to her heir, Rhea. She received the Pythian power after Cassie vanished, but is being held captive by the ancient gods, who found a way back to Earth and turned it into a wasteland.

With the help of John Pritkin, a powerful mage, Mircea Basarab, the sole survivor of the once-dreaded vampire senate, and a rag-tag group of survivors, Cassie must make the impossible happen. And find a way back to her own time to ensure that this one never takes place. But a whole pantheon stands in her way, and they will stop at nothing to wipe out the last remnant of her mother's blood, and the last chance Earth has for survival.