ARTICLE 1 - DEFINITION
It is a foul for intentional grounding if a passer, facing an imminent loss of yardage because of pressure from the defense, throws a forward pass without a realistic chance of completion. A realistic chance of completion is defined as a pass that lands in the direction and the vicinity of an originally eligible receiver.

Item 1. Passer or Ball Outside Tackle Position. Intentional grounding will not be called when a passer, who is outside, or has been outside, the tackle position throws a forward pass that lands at or beyond the line of scrimmage, even if no offensive player(s) have a realistic chance to catch the ball (including when the ball lands out of bounds over the sideline or endline). If the ball crosses the line of scrimmage (extended) beyond the sideline, there is no intentional grounding. If a loose ball leaves the area bordered by the tackles, this area no longer exists; if the ball is recovered, all intentional grounding rules apply as if the passer is outside this area.

http://operations.nfl.com/the-rules/2015-nfl-rulebook/

Pretty clear that ball needs to pass the LOS in the NFL as well.