A Mystery (Radio Waves)

When I drive home from work a little after 11 p.m., I like to listen to our local sports radio station here in Providence, 790AM, because they carry the Bob Valvano show and I get Sportscenter updates. What's mysterious is that every night, a country station overpowers the signal for a second every couple of seconds as I drive along. This never happens during the day. It only happens at night and only as I'm driving on RT 7. The signal briefly gets really strong near the church, then starts to disappear and is gone before I get home. I get totally different stations at 780AM and 800AM. No country or sports at all. The thing is, there is no 790AM that plays country anywhere around here. There is a station out of Edmonton, AB and one out of Columbus, OH. Neither of which I think I should be getting. I had a similar experience once driving on the Mass Pike back from Boston at about 2 a.m. where I picked both a Pennsylvania and an NYC station clear as day. It just doesn't seem possible that I would be picking up an Ohio station in Rhode Island. Even less likely that I'd get a Canadian station. I never hear call letters or ads or anything but music cycling in, so I can't get any clues as to where the station is coming from.