The 24-year-old joined Russell Slade's outfit at the start of September but only featured in three games before suffering a groin injury.
As he nears a return to full fitness, Slade has moved to secure the services of the former Sunderland stopper until December 10.
With fellow Spurs loanee David Button recuperating from a shoulder problem, Alnwick will hope to challenge Lee Butcher for his place between the sticks for Saturday's League One meeting with Bury.
Source: Team Talk
Source: Team Talk