分かる refers to the transformation from わかっていない to わかっている. So, even if you say もう分かる, it's still not yet わかっている. It rather means
the transformation from わかっていない to わかっている will already (succeed).
As an example:
The second sentence is strange because it implies you know the content of tomorrows' news! The first sentence is fine because it merely means "when the news comes out, the person will be able to understand it".
Answer to follow up question:
I don't understand then, why one can ask 「この言葉の意味はわかりますか？」. It doesn't mean "will you be able to understand the meaning of this word?", right? It means something more like "can you understand the meaning of this word?"
Whether you ask 「この言葉の意味はわかりますか？」 or 「この言葉の意味はわかっていますか？」 The answer to the question will be the same (the former asks "Are you able to perform the act of understanding this word? (transformation)" and the latter "Are you in the state of understanding what this word means?(state)" . Even though the rough meaning is the same, it can convey subtly different nuances.
For example, "この作業のやり方は分かりますか？" is the most neutral way to ask "Do you know how to do this task? (can I help?)". If you ask "この作業のやり方は分かっていますか？", then it may not have additional meanings, but it can also imply the speaker either thinks you should already know this, and is accusing you, or that you have already done the task and the speaker is unhappy with the result.
Here is another related example. When parents scold children, they will often say 分かってるの？ but never 分かるの for that purpose:
This sentence doesn't work if you say 分かるの？！ instead. The reason being that:
In the speaker's opinion, the transformation from わかっていない to わかっている here is obviously possible (because they are saying something completely reasonable, from their perspective). The question is whether the listener has bothered to perform this transformation so that they get in the state of having understood the consequence.
Contrast this with the following example:
Here, the speaker thinks the transformation from わかっていない to わかっている is not obvious. If they said これが餅職人の生き様だ！分かっているか？ it implies the listener already knows something about 餅職人の生き様 and it's odd why the speaker bothered to explain it immediately before. A more natural sentence in the second situation would be 餅職人の生き様ってもんが分かってんのか！？ (probably scolding a beginner 餅職人).