。
It looks like it'll turn to snow around evening.
Literal
Evening around-[at-には] snow become-[appearance-そうだ].
雪になる ('turn to snow') is the set phrase for weather transitioning — literally 'to become snow.' ~そうだ here is the appearance-based そうだ (from 'looks like'), distinct from the hearsay そうだ attached to plain forms. Built on the verb stem 雪になり+そう, which signals imminence: 'looks about to turn to snow.'