Rumours have been flying around for the last couple of weeks that Grayson was bringing Humphrey to Preston after the Jamaican winger's contrat expired at Motherwell.
He had favoured a move south of the border despite interest from Rangers. Leeds were also said to be interested but the 25 year old according to Sky Sports is undergoing a medical at Preston and a signing is imminent.
If the deal does materialise then Grayson will have four wingers to choos from with Monakana. Holmes and Hayhurst filling the wide slots last season.