I will be away for potentially a week, just to let everyone know.<br/><br/>It would depend what you are trying to achieve.  If you are in range and not actually trying to hit him, I'd say it is a freebie so to speak and no roll is required.  If you want a really close hit, a standard attack roll with one setback for poor conditions.  If you are out of range maybe a setback plus an upgrade, but with the understanding that damage isn't possible.