I really like the idea of this shot, with its foreground fence, its midground tree and its background moody sky. I like the darkness of the sky, gives it a brooding feel. Maybe the fence is a little too dark (would a GND filter have helped?).
It bothers me, though, that top of the fence on the right side is almost exactly at the midpoint. Because of this, I can't decide if I should look at the sky or the fence -- a what-is-the-subject sort of conflict. I think I would prefer the sky to be the subject, but the fence gets in my way.