In contrast, the Ospreys needed a win to secure their spot in the February 28th final. Now they must wait to see what happens in the remaining matches to see who will take on the runaway leaders.
It was the table-topping Blues who were always in control on a night when they further confirmed their rejuvenation. They took an early lead courtesy of a try from No.8 Aaron Atkins and a conversion and penalty from the outstanding Dean Gunter.
The Ospreys hit back with an unconverted try from centre Rhys Llewellyn before the break but the Blues totally dominated the second half and scored a further try through the impressive Gunter, which he duly converted.
The Ospreys managed a consolation penalty from Chris Banfield but it was too little too late.
Blues Regional Performance Manager Gafyn Cooper was impressed with each side, stating: "Both teams tried to play a running game on a heavy pitch and I take my hat off to that."
Blues North now wait to see who they will meet in the final of the U16 competition, which will be either Ospreys or Scarlets.
Blues South Under 16s will play Ospreys in a re-arranged game tomorrow (Wednesday 24th Jan) at University of Glamorgan Playing Fields, Treforest, kick-off 715pm.