POP UP TFC.

Narrative

AFTER RECEIVING SEVERAL WX BRIEFINGS WITH THE LOWEST CEILING RPTED AS OCNL 1500 FT OVCST. MY STUDENT AND I TOOK OFF FROM PNE FOR SOME LCL PATTERN WORK. UPON REACHING 1100 FT MSL; IT WAS APPARENT THAT THE CEILING WAS LOWER THAN RPTED AND THAT WE WOULD NOT BE ABLE TO MAINTAIN REQUIRED CLOUD CLRNC. WE ADVISED TWR THAT WE WERE INBOUND; AND WE WERE CLRED TO LAND RWY 24. WE LOST SIGHT OF THE ARPT AND THEN ADVISED TWR THAT WE'D LIKE TO SWITCH TO PHL APCH. AFTER APPROVAL; WE FLEW OVER RWY 24; WHICH WAS NOW IN SIGHT; BUT RATHER THAN CONDUCTING AN UNSTABLE APCH; WE CALLED APCH AND ASKED IF THEY COULD VECTOR US BACK FOR THE ILS RWY 24. THE CTLR ASKED IF WE COULD MAINTAIN VFR AT 2000 FT. I RESPONDED; 'NEGATIVE;' AND WAS TOLD THAT HE COULD NOT VECTOR ME; THEN. I THEN ASKED TO FILE AN IFR CLRNC INTO PNE. THE CTLR GRANTED MY REQUEST; WITH THE ADMONISHMENT THAT I SHOULD HAVE FILED BEFORE DEPARTING. WE WERE THEN VECTORED AND LANDED UNEVENTFULLY. THE REASON FOR MY RPT IS TO EXPRESS MY AGREEMENT WITH THE CTLR'S ADVICE ON PREDEP FILING. THAT IS MY NORMAL PROC; BUT; BASED ON THE ATIS AT THE TIME OF DEP; I FELT THAT WE WOULD HAVE ADEQUATE CLOUD CLRNC. ON FUTURE TRAINING FLTS; WITH MARGINAL WX RPTED; I'LL TAKE THE EXTRA TIME TO FILE.