I have that antenna (radio shack mag mount) stuck to a metal heater by my window. It is very effective with any scanner I connect to it. Since you are receiving most of the freqs you want to hear except for some static, this antenna should do the trick.
Although some here would disagree, you could try removing or rearranging the sections of the radio shack mag mount (if you do get it) and see if it works even better. I have had some strange luck playing with antennas and scanners. You could even try taking a piece of wire, stripping the end, and attaching it to the telescopic whip that is already on the scanner. Then, try placing the wire in the window with a suction cup or taping it. Sometimes, strange "magic" will make a simple thing like some wire on your existing antenna work better. It may defy what the experts say, but it doesn't cost anything to grab a piece of wire lying around the house. Have fun!