THE NON-INSTRUMENT RATED PLT (RECENTLY CERTIFIED IN CANADA AS A PVT PLT) RCVD A WX BRIEFING FM A FSS & FILED A VFR FLT PLAN TO PORTLAND, OR. HE WAS BRIEFED ON MOD TURBC, LGT TO MOD ICING, MOUNTAIN OBSCURATIONS & MARGINAL VFR TO IFR CEILINGS AT THE DESTINATION. ALSO, HE WAS ADVISED THAT VFR WAS NOT RECOMMENDED. WHEN THE FLT WAS ABOUT 20 MI EAST OF PORTLAND ARPT, THE PILOT CONTACTED ATC & WAS ADVISED TO MAINTAIN VFR AT 2000 FT FOR LNDG STRAIGHT-IN AT PORTLAND. ABOUT 2 MIN LATER, HE RPRTD HE WAS DSCNDG TO 1200 FT TO REMAIN VFR. SHORTLY THEREAFTER, HE ENCOUNTERED WX & INITIATED A CLIMB IN IMC. HOWEVER, DURING THE CLIMB, THE ACFT STALLED, THEN DESCENDED OUT OF CONTROL UNTIL IMPACT WITH TREES AT 1200 FT MSL. ABOUT 9 MI WEST AT THE TROUTDALE ARPT (ELEV 36 FT), THE 1518 PDT WX WAS IN PART: 1200 FT OVC, 3 MI VIS WITH MOD RAIN, WIND FROM 230 DEG AT 6 KTS.