I was driving to where I have equipment co-located, traveling east bound on Highway 90, just past Mercer Island, just into Bellevue (Washington), monitoring 87.9 because I had picked up a pirate station in downtown Bellevue a week prior.

The station I had picked up in downtown was extremely weak, receivable for only a few blocks so it may even actually been legal (the radio in my car is very sensitive).

But this was something totally different.  It rapidly faded in, in about 1-2 seconds, just east of Mercer Island, it was playing a Viagra commercial, it was rock solid from about the I-405 interchange to the East Gate exit, where it faded out equally fast as it had faded in.

There are only two legal stations on this frequency in the US, one is a whopping 10 watts at a high school in California, the other 28 watts at a church in Nevada.

When I came back from the co-lo facility, it was gone.  Maybe something breaking through form a parallel dimension .. (Twilight Zone music)