The 19-year-old, who signed a four-year extension to his United contract in December, goes straight into the North End squad in time for Tuesday's trip to Peterborough.
Manchester-born Welbeck, who becomes Darren Ferguson's first signing as Preston boss, has scored five goals in 24 appearances for United.
Paternal interest: Welbeck will be managed by Ferguson Jnr at Deepdale
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