I think that is a combination of these answers. Maybe and probably neither mean yes nor no BUT. If I said it "it probably will" I would say that there is more certainty that is will than if I say "maybe it will".
It will probably snow tomorrow. Maybe it will snow tomorrow. The first = there is an 80/90% chance of snow. The second = there is a 50% chance of snow.
This can work the other way too - "it probably won't" or "maybe it won't"
It probably won't snow = there is a only a 10% chance of snow. Maybe it won't snow = there is a 40-50% chance of snow. (sometimes the last example is used if you are hoping that there won't be snow too!)
Probably is further towards the end of BOTH ends of the gradient line between yes or now, than maybe. Maybe is closer to the centre.