Can I use 'possibly' instead of 'probably'?

Native speaker’s answer
Rebecca
Yes, you can! In this context, they mean similar things. Note that "probably" has a stronger sense of certainty than "possibly" does, however. Thus, "most likely" should be used instead as it's closer in meaning to "probably." Ex: A: Will you be coming on vacation with us? B: Probably. Ex: A: When can you submit your essay? B: Tomorrow, most likely.