In some situations it can be translated literally with "a venire", as in "years to come" -> "anni a venire". This however works mainly with time expressions (I'm sorry I cannot think of an hard and fast rule).
In all other cases you have to translate less literally by using periphrases and in generally restructuring the sentence. This is how I'd translate your example sentence:
Nel centro dobbiamo aspettarci un tempo più brutto: parecchie tempeste lungo la parte mediana del paese accompagnate da pioggia molto forte, con tuttavia degli sprazzi di sereno.
As you can see I translated "We've got worse to come in terms of weather" as "Dobbiamo aspettarci un tempo più brutto" that is "we should expect a worse weather".
(This sentence sounds a little clunky to me honestly, I probably would rather say "delle giornate più brutte" but I wanted to stay as close as possible to the example you provided).