THE WEATHER BRIEFER INFORMED THE PILOT THAT VFR WAS NOT RECOMMENDED DUE TO CURRENT/FORECAST CONDTIONS. THE NON INSTRUMENT RATED PILOT THEN FILED A VFR FLIGHT PLAN RESPONDING THAT HE WAS IFR RATED AND WOULD FILE INFLIGHT IF NECESSARY. WITNESSES REPORTED OBSERVING THE AIRCRAFT CRUISING NORTHBOUND OVER I-5 AT A MODERATE SPEED AND LOW ALTITUDE BENEATH THE CLOUDS. WEATHER CONDITIONS IN THE VICINITY OF THE ACCIDENT SITE WERE DESCRIBED AS 300 FOOT CEILING AND 1 MILE VISIBILITY. DARK NIGHT CONDITIONS EXISTED WHEN THE AIRCRAFT STRUCK POWER LINE 75 FEET ABOVE THE I-5 MEDIAN AND 6 NAUTICAL MILES SOUTH OF THE DESTINATION AIRPORT. IN SPITE OF DETERIORATING WEATHER CONDITIONS THE PILOT MADE NO ATTEMPT TO DIVERT ALONG HIS ROUTE OF FLIGHT TO A MORE FAVORABLE DESTINATION. AN ENTRY REFERRING TO 'SCUD FLYING' WAS NOTED IN THE PILOT'S LOGBOOK.