Learn Hardcore Dutch: Wij wachten binnen tot de storm voorbij is.

Dutch often puts the main verb followed by adverbs of manner, place or time. So wachten (to wait) comes first, then binnen (inside). You could also say Wij wachten vandaag binnen, putting a time adverb (vandaag) before the place adverb, but place adverbs normally follow the verb directly.

What role does tot play in this sentence?

Tot here is a subordinating conjunction meaning until. It introduces a time-clause (tot de storm voorbij is) that indicates when the action of waiting ends.

Could we use totdat instead of tot?

Yes, in spoken Dutch you often hear totdat de storm voorbij is. Formally, both tot and totdat are correct as conjunctions meaning until. Tot is slightly more concise, while totdat can feel a bit more emphatic.

Why does is appear at the end of the subordinate clause?

In Dutch subordinate clauses the finite verb moves to the end. Since tot introduces a subordinate clause, is (the finite verb) must go to the very end: tot de storm voorbij is.

What exactly does voorbij mean here?

Voorbij is an adverb meaning over, past, or finished. In de storm voorbij is it means the storm is over or the storm has passed.

Can you shorten Wij to We?

Yes, Wij (we) is the full pronoun and We is the colloquial short form. You can say We wachten binnen tot de storm voorbij is in everyday speech.

Could you rephrase the ending with is voorbij instead of voorbij is?

Not in a subordinate clause. In main clauses you can say De storm is voorbij (The storm is over). But after tot, which creates a subordinate clause, you must place the verb at the end: tot de storm voorbij is.