Learn German: Ich bin noch wach, obwohl es schon spät ist. - I am still awake although it is already late.

Because obwohl (although) is a subordinating conjunction. In German, these types of connecting words push the conjugated verb (here, ist) to the very end of their clause.

Can I flip the sentence and start with obwohl?

Yes, you can! You could say: Obwohl es schon spät ist, bin ich noch wach. Notice that when the obwohl clause comes first, the main clause right after the comma must start with its verb (bin).

What do noch and schon add to this sentence?

noch means still and schon means already. They are often used together in sentences like this to emphasize the contrast: the fact that it is already late makes it surprising that the person is still awake.

Is the comma before obwohl mandatory?

Yes! Unlike in English where commas before although can sometimes be optional, German strictly requires a comma to separate a main clause from a subordinate clause.