FM Radio Station Signals are "Line of Sight".  This means that if anything is between you and the transmitter, you will have problems hearing an FM radio station.  For example:  When the Apollo Astronauts went to the moon, they used FM communication.  They used a 2 Watt Transmitter to communicate with Earth, and not all that power was needed because there is nothing between here and the moon. 

Here on the ground we have mountains to content with and no matter how much power you throw at a mountain, that FM signal is not going to get through.  This is why we employ over 17 transmitters, to carry our signals into nearly every nook and cranny in the tri-state area.