Found the following mention of a white raven in Fairbanks: (http://www.ewebtribe.com/NACulture/articles/ADNWhtRavenFbx.htm). Maybe it had some mixed color offspring.
Other birds that came up in my search include the swallow-tailed kite. Large black and white hawklike bird 22 inches long, weight about 40% of a raven. But it would be thousands of miles out of range.
Maybe you have an accidental from Asia. (Watch out for the bird flu.)
You might try ABR Inc. there in Fairbanks. They've got some bird experts on staff.
Not a raptor. Not the 'white' raven. Still thinking magpie, somebody's pet bird that got out.