Tower Controller witnessed a near separation event when the Local Controller failed to recognize the developing conflict. The reporter expressed concern regarding the facilities training and certification procedures.

Narrative

Small aircraft was on final approach for Runway 31 prior to the threshold with a full stop landing clearance. Local Control had 2 military jets at high key for Runway 31. I did not have the whole picture because from Ground Control you can not see the bright but I was paying attention to the traffic situation. I looked out the window and observed the jets at low key. I looked at the approach path for Runway 31 and saw aircraft on short final. I told the Controller on local that it was not going to work. He looked at me with a blank stare. I told him that he has a guy on final and it is not going to work. He then issued a restricted low approach to the jets of at or above 600 FT. The lead jet was already below 400 FT and on short final. The previous aircraft at this point was still on landing roll out about 2;000 down the runway. Recommendation; FAA needs to stop pushing new trainees through positions to fulfill staffing shortages. FAA needs to amend the training order to make it mandatory that a trainee have several documented moderate to heavy training sessions in which they applied air traffic rules and regulations without any infractions. Just prior to the Local Controller's certification on local; I trained him. He did not perform to a standard that I would consider certifiable as a Tower CPC. I was very surprised to come back from a break and find him checked out through the Tower knowing that I just wrote him up for not using vehicle on runway strips and for excluding the vehicle on runway from the position relief briefing.