Former Championship top goalscorer McCormack, who has 13 caps for Scotland, will reportedly join City on loan after being left out of Villa's first-team plans.
City are in desperate need of a striker - with Fornaroli set to be sidelined until at least January - and are now set to turn to the 31-year-old McCormack, whose former clubs include Fulham and Leeds United.
Villa, who are home to Socceroos captain Mile Jedinak and Jordan Lyden, have decided to let the striker move to Australia, with manager Steve Bruce revealing the move was imminent.
"I believe the clubs have agreed (Villa and Melbourne City). It’s over to Ross (now)," Bruce said after his side's 2-1 win over Nottingham Forest on Sunday morning (AEST).
"I wish him the best of luck no matter what people think and all the rest of it.
"He needs to go and play and get himself in the right condition for it. It could be the perfect fit for him."
McCormack has netted just three goals for Villa since a big money £12 million (A$20.5 million) move from Fulham in August 2016 and had a high-profile falling out with Bruce after missing training last season.