The academy graduate has made just one first-team appearance against Fulham under-21s in the Checkatrade Trophy this season and played deputy to Luke McGee.
Following Stephen Henderson's arrival from Nottingham Forest on transfer deadline day, Bass has now slipped to third choice in Kenny Jackett's goalkeeping pecking order.
As a result, it means the Blues can allow the 20-year-old to leave Fratton Park on a temporary basis to gain more first-team experience.
Boss Jackett said: 'It gives us the opportunity to let Alex Bass go out on loan and gain some experience.
'His whole season without first-team football wouldn't necessarily help his development.
'I would think it would be a non-league side and after 28 days you can have a recall.'