If your (foreign) bank account was still open as of December 31st (the end of the tax year for the current filing season) then you would indicate that the account is still active, on Form 8938, even if you subsequently closed the account in the current calendar year (i.e., next year's tax filing year). However, in the tax year in which you close the bank account, there is a place on Form 8938 to explicitly disclose that fact. Please see the screen-capture images below this text for a visual illustration (simply click the images to open).
You would be asked what the maximum value of the account was during the year (and so during the time that it was open); but to answer your main question, the "current" balance of the closed account would, naturally, be $0 . . . if the account is actually closed, as of the end of the relevant tax year.
Certainly, though, that (closed) account's balance, if transferred to a newly-opened foreign bank account, will be separately reported as such on Form 8938, along with the actual balance.
Hopefully that answer makes sense for you; foreign accounts and the tax laws can be especially confusing sometimes. Thank you for asking this question.
