AIR TOUR ACFT ENCOUNTERS WX; MUST AVOID BY CLBING ABOVE CLOUDS.

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I WAS CAPT OF AN SMT FLT THAT DEPARTED LAS; NV; IN GOOD VFR CONDITIONS. THE GRAND CANYON ARPT WAS ALSO RPTING VFR. WE DEPARTED WITH A 1-WAY FUEL LOAD. APPROX 1 HR INTO THE FLT; ON THE SFAR 50-2 'BLUE-1' AIR TOUR RTE AT 7500 FT MSL; AND JUST PAST OUR POINT OF NO RETURN; E OF MOUNT DELLENBAUGH; WE ENCOUNTERED INCREASING CLOUDINESS; LOWERING CEILINGS; AND REDUCED VISIBILITY; THOUGH IT WAS STILL TECHNICALLY VFR. I REQUESTED PIREPS FROM 4 COMPANY ACFT ALSO ON THE TOUR RTE; JUST MINS AHEAD OF US. I WAS REPEATEDLY TOLD THAT 'IT'S NO PROB; IT'S GOOD VFR; AND ONLY MINOR DEVS ARE NECESSARY.' IT WAS NOT. IT NOT ONLY GOT PROGRESSIVELY WORSE; BUT WE ENDED UP IN THE CLOUDS. I TURNED THE ACFT TOWARD LOWER TERRAIN AND CLBED TO VFR CONDITIONS ON TOP OF THE LOWER SCUD; WITH RAGGED CEILINGS ABOVE; AT 8200 FT MSL. I MIGHT HAVE GONE HIGHER; EXCEPT THAT COMPANY TFC WAS RPTED OPPOSITE DIRECTION ON THE 'REVERSE AIR TOUR' AT 8500 FT MSL. BY 40 NM WNW OF GRAND CANYON WE WERE AGAIN LEGALLY VFR AND PROCEEDED WITHOUT FURTHER INCIDENT. IT IS NOT MY CUSTOM TO GET TRAPPED LIKE THIS; HAPHAZARDLY; IN MARGINAL CONDITIONS WITH MINIMAL FUEL SUPPLIES. IN THE PAST; I HAVE ENDURED THE SCORN OF MGMNT; DISPATCHERS; AND 'OLD TIME CANYON PLTS' FOR PUTTING ON EXTRA FUEL AND HAVING AN IFR FLT PLAN ON FILE. BUT THIS SIT WAS AGGRAVATED BY THE OVERLY OPTIMISTIC AND MISLEADING RPTS OF OTHER PLTS.