INSTRUCTOR PLT TRIES SVFR FOR PATTERN WORK. WX MOVES IN SO FAST FLT ASSIST NEEDED TO NEARBY ARPT.

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I OBTAINED A WX BRIEFING THROUGH DUAT. VFR WAS FORECAST ALL DAY. I LISTENED TO ATIS. IT RPTED 10000 BROKEN VISIBILITY 10 MI. AFTER WE PREFLTED THE AIRPLANE; CONDITIONS HAD CHANGED TO 5000 BROKEN VISIBILITY 2 1/2 MI. AS WE WERE GOING TO BE CONDUCTING TOUCH-AND-GOES IN THE TFC PATTERN; I ASKED FOR A SPECIAL VFR CLRNC; WHICH I RECEIVED. IN MY JUDGEMENT 2 1/2 MI AND 5000 BROKEN WOULD BE SUFFICIENT. AFTER WE TOOK OFF; I COULD SEE CLOUDS AHEAD SO WE TURNED XWIND. I COULD SEE CLOUDS BENEATH ME SO I TURNED DOWNWIND TO TRY TO RETURN FOR LNDG (I COULD SEE THE APCH END OF THE RWY WE HAD JUST DEPARTED). I TURNED BASE BUT I COULD NOT SEE THE END OF THE RWY AS THERE WAS A CLOUD BANK BTWN US. I STAYED ON TOP AND TRIED ANOTHER RWY BUT IT TOO BECAME OBSCURED BY THE TIME I WAS ON FINAL. I CIRCLED AND CLBED UNTIL I WAS WELL ABOVE THE CLOUDS AND TWR ASSISTED ME TO A NEARBY ARPT (UNCTLED) WHERE I WAS ABLE TO MAKE A VFR LNDG. THE CAUSE FOR THIS SITUATION WAS THE UNFORECAST LOW CEILING WHICH WERE DRASTICALLY DIFFERENT TO WHAT HAD BEEN RPTED BY ATIS. THERE IS A WX RPTING STATION AT THE ARPT AND I DID NOT EXPECT SUCH A DISCREPANCY.