There is no possibility.
The closest star to the WOW signal is Tau Sagittarii, which is 122 light years away. This means that the signal (assuming that it is actually from outer space) must have been sent at least 122 years before 1977, which is 1855.
A second problem is that the signal was recieved before the launch. Common sense dictates that congratulations should have been recieved after the event.
Also, if aliens were close enough to Earth to observe the launch, why would they go through the trouble of send the message from the home planet 122 light-years away (and in the past)?
Also, why would they send congratulations for voyager 1? Why not voyager 2, which actually launched before voyager 1?