I'm not surprised that obstructions close in scatter signals. Additional height and / or higher gain antenna are the two options to consider. (In order of preference)
If going to a larger antenna, go all the way. A Winegard HD7698P or a combination of an Antennas Direct 91XG and Antennacraft Y10713 joined with UVSJ.
http://www.winegarddirect.com/viewit...P%29&p=HD7698P
http://www.antennasdirect.com/store/...V_Antenna.html
http://www.antennacraft.net/Antennas/AntennasVHF.html
http://www.antennasdirect.com/store/..._combiner.html
There are plenty of alternate retail outlets to shop from... Amazon, SolidSignal, Frys, Best Buy, etc.