。
I really hope it clears up tomorrow.
Literal
Tomorrow [topic-は] clear-up-for-me [if-と] good [wish-なぁ].
晴れてくれるといいなぁ — 'if it would clear up for me, it would be good.' ~てくれる personifies the weather, treating sunshine as a favor done for the speaker. The elongated なぁ (with the chōon) adds a wistful, longing quality to the wish.