ALTHOUGH WEATHER CONDITIONS WERE MARGINALLY VFR AT HIS DEPARTURE POINT, AND THE PILOT HAD ACCESS TO A VEHICLE WHICH COULD HAVE BEEN USED TO DRIVE TO HIS DEST, HE DEPARTED NOVATO, CA, ENROUTE TO LAKEPORT, CA, WITHOUT OBTAINING A WX BRIEFING NOR FILING A FLT PLAN. SHORTLY AFT DEPARTURE AND AGAIN NEARING HIS DEST HE RECEIVED INFLT WX INFO FM UKIAH FSS AND ACKNOWLEDGED THE REPORTED BAD WX IN THE VIC OF HIS ROUTE OF FLT. A WITNESS NEAR THE ACCD SITE REPORTED SNOW, STRONG WINDS, LOW CEILINGS, AND WORSENING CONDITIONS AT THE TIME OF THE ACCD. THE ACFT COLLIDED WITH A SHALLOW RIDGE IN LOW MOUNTAINOUS TERRAIN WHILE IN AN UPRIGHT, SLIGHTLY DESCENDING RIGHT WING DOWN ATTITUDE. THE ELEVATION OF THE GROUND IMPACT SITE WAS APPROXIMATELY 2450 FEET AND THE CLOUD BASES WERE REPORTED AT UKIAH AS APPROXIMATELY 2600 FEET MSL NEAR THE TIME OF THE ACCD.