C170 PLT RUNS INTO FOUL WX ENRTE GUP TO SDL. PICKS UP IFR CLB AND ICE; DSNDS; CANCELS IFR AND HAS TO GET RADAR VECTORS FOR A DIVERSION TO ALTERNATE AT PAYSON; AZ. SUGGESTS THAT WX BTWN TWO WX RPTING POINTS MAY VARY; SIGNIFICANTLY.

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I DEPARTED GUP ON A VFR FLT TO SDL AT APPROX PM30 LCL TIME. I PROCEEDED SW TOWARD BETTER WX CONDITIONS THAN THE DIRECT RTE I HAD FILED FOR MY VFR FLT PLAN. AS I TURNED TO A SOUTHERLY HEADING IT BECAME CLR TO ME THAT CONTINUED VFR TOWARDS SDL WAS IMPROBABLE. I CALLED ZAB AND PICKED UP AN IFR CLRNC INTO SEDONA. ATC ISSUED ME A CLB TO 10700 FT INTO MINIMUM VECTORING ALT. AS I CONTINUED THE CLB; OUT OF ABOUT 10000 FT I STARTED TO PICK UP A TRACE OF CLR ICE. AT THIS POINT I ELECTED TO CANCEL MY IFR CLRNC AND DSND BACK INTO LOWER ALT (I COULD SEE DOWN THROUGH BROKEN CLOUDS TO GOOD VISUAL GND CONTACT). I TURNED NE TOWARD WINSLOW TO FIND THAT CONTINUED VFR FLT WAS IMPROBABLE. I WAS LEFT WITH THE SIT OF LOWERING CLOUDS; DARKENING SKIES AND FUEL BECOMING A FACTOR. I PICKED UP A SOUTHERLY HEADING AND AFTER SEVERAL MINS CONTACTED CTR FOR RADAR VECTORS INTO PAYSON (E69). AFTER SWITCHING TO A DIFFERENT CTLR; THE CTLR WAS RELUCTANT TO HELP BECAUSE OF MY LOW ALT AND HIS LIMITED RADAR COVERAGE IN THAT AREA. I FINALLY INSISTED UPON 'SUGGESTED RADAR HEADINGS TO FIND THE ARPT.' USING THE INTERMITTENT RADAR RETURNS THE CTLR WAS ABLE TO GIVE ME HEADINGS TO THE ARPT. THE ARPT SITS ON THE S SIDE OF A HILL AND WAS DIFFICULT TO SEE FROM THE DIRECTION I WAS APCHING. ALL'S WELL THAT ENDS WELL -- BUT -- WITHOUT ATC'S HELP I HATE TO THINK WHAT COULD HAVE HAPPENED. I HAVE FLOWN IN COLORADO; WYOMING; UTAH; MONTANA AS WELL AS ALASKA IN MY SMALL SINGLE ENG ACFT. I HAVE FLOWN TO NUMEROUS POINTS ALL OVER THE WORLD IN JET ACFT BUT I HAVE NEVER HAD A MORE CHALLENGING FLT THAN THAT EVENING UP ON THE MOGOLLON RIM NE OF PHOENIX. THE LESSON LEARNED -- THE SPRING TIME WX MAY BE OK IN PHX AND GUP BUT THE WX UP ON THE 'RIM' MAY NOT. I DO NOT THINK I BROKE ANY RULE BUT I'LL NEVER DO THIS AGAIN.