If Judita hands in her paper early tomorrow, she'll probably get an A.
If Judita hands in her paper early tomorrow, she may get an A.
What's the likely context of the two? I guess in the first case the speaker probably have already seen Judita's paper, whereas in the second case he haven't. Someone told me it's just a matter of degree, where the probability of 'probably', say 80%, is greater than 40%, that of 'may'. But I feel that there's some fundamental or qualitative change occuring when 'may' is replaced by 'probably'.