Justin Georcelin, 33, was last seen in his room at Springhill between 11.30pm on Sunday June 18 and 12.15am on Monday June 19.
Police believe he left the open prison at around 12.40am on Monday.
Georcelin is mixed race, 6ft, and of medium build.
He has short black hair, brown eyes and a goatee beard.
Georcelin has links to Northamptonshire and was described by a Northamptonshire judge in 2006 as ‘a danger to the public’ after he was sentenced for being part of a group that robbed two taxi drivers at knifepoint in the county.
Investigating officer Detective Constable Carolyn Bailey said: “We are working to trace Justin Georcelin as soon as possible and are appealing for the public’s help to report any sightings.
“Anyone who sees Georcelin should not approach him but should instead call 999.”